Operation Iceberg

From “Last Battle” to the Next War: Using Operation
ICEBERG to Inform Multi-Domain Battle in the

Indo-Asia Pacific
A Monograph
by
MAJ Jonathan C. Leiter
US Army
School of Advanced Military Studies

US Army Command and General Staff College
Fort Leavenworth, KS
2018
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From “Last Battle” to the Next War:
Using Operation ICEBERG to Inform Multi-Domain Battle in the 5b. GRANT NUMBER
Indo-Asia Pacific
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Major Jonathan C. Leiter
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14. ABSTRACT
This monograph examines Operation ICEBERG, the 1945 campaign to invade the Japanese-held Ryukyu Islands, most notably
Okinawa, to inform how the United States Army could employ its land combat forces in Multi-Domain Battle in the Indo-Asia
Pacific region. The monograph reviews the Multi-Domain Battle Concept, then employs historical case study to describe the
campaign, focusing on elements reflected in both. The investigation reveals examples of cross-domain maneuver in support of
operations in the maritime domain, land forces enabling long-range fires, and strategic, operational, and tactical convergence
creating a “window of advantage” for ground maneuver. It also identifies a situation where the failure to employ cross-domain
maneuver likely prolonged the campaign. It then offers informed recommendations for the development of Multi-Domain
Battle in the Indo-Asian Pacific and posits questions for further study.
15. SUBJECT TERMS

Multi-Domain Battle; Indo-Asia Pacific; Operation ICEBERG; Okinawa; Convergence
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OF ABSTRACT OF PAGES Major Jonathan C. Leiter
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Name of Candidate: Major Jonathan C. Leiter
Monograph Title: From “Last Battle” to the Next War: Using Operation ICEBERG to Inform
Multi-Domain Battle in the Indo-Asia Pacific
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__________________________________, Monograph Director

John M. Curatola, PhD
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___________________________________, Director, Graduate Degree Programs

Robert F. Baumann, PhD
The opinions and conclusions expressed herein are those of the student author and do not
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ii
Abstract
From “Last Battle” to the Next War: Using Operation ICEBERG to Inform Multi-Domain Battle
in the Indo-Asia Pacific, by MAJ Jonathan C. Leiter, US Army, 53 pages.
This monograph examines Operation ICEBERG, the 1945 campaign to invade the Japanese-held
Ryukyu Islands, most notably Okinawa, to inform how the US Army could employ its land
combat forces in Multi-Domain Battle in the Indo-Asia Pacific region. The monograph reviews
the Multi-Domain Battle Concept, then employs historical case study to describe the campaign,
focusing on elements reflected in both. The investigation reveals examples of cross-domain
maneuver in support of operations in the maritime domain, land forces enabling long-range fires,
and strategic, operational, and tactical convergence creating a “window of advantage” for ground
maneuver. It also identifies a situation where the failure to employ cross-domain maneuver likely
prolonged the campaign. It then offers informed recommendations for the development of Multi-
Domain Battle in the Indo-Asian Pacific and posits questions for further study.
iii
Contents
Abstract .......................................................................................................................................... iii
Contents ...........................................................................................................................................iv
Acknowledgments ...........................................................................................................................vi
Acronyms ...................................................................................................................................... vii
Illustrations ................................................................................................................................... viii
Introduction ...................................................................................................................................... 1
The Problem ................................................................................................................................ 3
The Research Question ............................................................................................................... 6
Secondary Questions ................................................................................................................... 6
Assumptions................................................................................................................................ 7
Operation ICEBERG: Proto-Multi-Domain Battle in the Indo-Asia Pacific .............................. 8
Scope and Limitations and Delimitations ................................................................................... 9
Multi-Domain Battle ...................................................................................................................... 11
Introduction ............................................................................................................................... 11
Competition vs. Armed Conflict ............................................................................................... 12
The Expanded Battlespace ........................................................................................................ 14
Calibrate Force Posture: ............................................................................................................ 15
Employ Resilient Formations: .................................................................................................. 15
Converge Capabilities: .............................................................................................................. 16
Case Study ...................................................................................................................................... 17
Operation ICEBERG ................................................................................................................ 17
The Joint Operations Area (JOA) ............................................................................................. 17
The Belligerents ........................................................................................................................ 21
Immediate Military Objectives of Operation ICEBERG .......................................................... 26
iv
Planning and Preparation; 10 August 1944 to 10 October 1944 ............................................... 26
Preliminary Operations; 10 October 1944 to 31 March 1945 ................................................... 30
Preliminary Landings; 26 March 1945 to 31 March 1945 ........................................................ 34
The Battle of Okinawa; 1 April 1945 to 23 June 1945 ............................................................. 37
Analysis and Recommendations..................................................................................................... 45
Convergence in Operation ICEBERG ...................................................................................... 46
Recommendations ..................................................................................................................... 50
Questions for Further Study ...................................................................................................... 52
Conclusion ................................................................................................................................ 53
Bibliography ................................................................................................................................... 54
Print Sources ............................................................................................................................. 54
Online Sources .......................................................................................................................... 55
Academic Publications.............................................................................................................. 56
v
Acknowledgments
I wish to express my gratitude to the individuals who contributed to this work. To my
director, Dr. John Curatola for his patience and his open door. To my seminar leader, COL Keith
Pruitt for his constant encouragement to “finish the thing.” To my classmates for always listening
and acting interested. Finally, to my wonderful wife, Carie, also a full-time student, and my
daughters Adelyn and Eliza. Thank you for understanding that sometimes my door has to be shut
and loving me anyway…
vi
Acronyms
A2/AD Anti-Access and Area Denial
AAF Army Air Forces
AO Area of Operations
AUSA Association of the United States Army
BCT Brigade Combat Team
BLT Battalion Landing Team
CATF Commander of the Amphibious Task Force
CinCPOA Commander in Chief, Pacific Ocean Areas
CLF Commander of the Landing Force
IJA Imperial Japanese Army
IJN Imperial Japanese Navy
JCS Joint Chiefs of Staff
JOA Joint Operations Area
JTF Joint Task Force
LTG Lieutenant General
MDB Multi-Domain Battle
PACOM United States Pacific Command
TF Task Force
TRADOC United States Army Training and Doctrine Command
USARPAC United States Army Pacific
vii
Illustrations
Figure 1. The Multi-Domain Battle Operational Framework......................................................... 14
Figure 2. The Island of Okinawa .................................................................................................... 20
Figure 3. Japanese Thirty Second Army Defensive Dispositions, 1 April 1945 ............................ 22
Figure 4. Organization of Central Pacific Task Force .................................................................... 24
Figure 5. Organization of Expeditionary Troops for the Ryukyus Campaign, January 1945 ........ 25
Figure 6. Allied Invasions of Iwo Jima and Okinawa .................................................................... 34
Figure 7. Kerama Islands................................................................................................................ 35
Figure 8. Operations in Southern Okinawa .................................................................................... 44
Figure 9. Converging Capabilities in Operation ICEBERG........................................................... 47
viii
Introduction
Historical examples clarify everything and also provide the best kind of proof in the
empirical sciences. This is particularly true of the art of war.
-Clausewitz, On War
In his Eisenhower Luncheon remarks at the 2016 Association of the United States Army
(AUSA) Conference, General Mark Milley, the 39th Chief of Staff of the United States Army,
predicted that fundamental changes to the global order and emerging trends and technologies
threaten to erode the US military’s overmatch and will likely “result in the most significant and
profound change in the character of war we have witnessed throughout all of recorded history.” 1
Milley believes that future enemy anti-access and area denial (A2/AD) weapons will be of
sufficient quantity and capability to contest the air and sea superiority US forces have become
dependent upon. The 2018 National Defense Strategy (NDS) reinforces his assessment, observing
that “today, every domain is contested- air, land, sea, space, and cyberspace.” 2 These ominous
predictions appear corroborated by observing Russian units in Ukraine in 2014 and recent
Chinese military actions in the South and East China Seas. If true, they challenge the foundational
assumptions which underlie the last twenty-five years of land warfare theory, and US Army
doctrine and force structure development. General David Perkins, the Commander of United
States Army Training and Doctrine Command (TRADOC) observed that “During most of our
1
Mark A. Milley, "State of the Army Address" (speech, Association of the United States Army
2016 Annual Meeting and Exposition, Walter E. Washington Convention Center, Washington, DC,
October, 2016).
2
US Department of Defense, Summary of the 2018 National Defense Strategy of The United
States of America: Sharpening the American Military’s Competitive Edge (Washington, DC: Office of the
Secretary of Defense, 2018), 3.
1
recent history, the only domain that has been truly contested has been the land domain.” 3 Left
unaddressed, these developments threaten to leave the United States with an army “not
sufficiently trained, organized, equipped, nor postured to deter or defeat highly capable peer
enemies to win in future war.” 4
To counter these threats, the United States Army, Marine Corps, and Air Force have
cooperated since 2015 to develop a new operational concept for the employment of future land
forces; Multi-Domain Battle: Evolution of Combined Arms for the 21st Century. 5 Multi-Domain
Battle (MDB) is “an operational concept with strategic and tactical implications.” 6 Using the
Army and Marine Corps operating concepts as starting points, the MDB concept seeks to describe
how future land forces, as a component of the Joint Force, should be employed short of war, turn
denied spaces into contested spaces, defeat adversary campaigns, and consolidate their gains. 7
To accomplish these objectives, an MDB approach employs three interrelated
components; calibrated force posture, resilient formations, and converging capabilities. An
expanded operational framework visualizes the convergence of capabilities spatially, temporally,
and across domains to produce “windows of advantage that enable freedom of maneuver to defeat
enemy systems and achieve friendly objectives outright.” 8
3
David G. Perkins, "Multi-Domain Battle: Joint Combined Arms Concept for the 21st Century,"
AUSA.org, November 14, 2016, accessed 21 October 2017, https://www.ausa.org/articles/multi-domain-
battle-joint-combined-arms-concept-21st-century.
4
"Multi-Domain Battle White Paper," www.tradoc.army.mil, February 24, 2017, 3, accessed 27
August 2017, www.tradoc.army.mil/multidomainbattle/docs/MDB_WhitePaper.pdf.
5
Kelly McCoy, “The Road to Multi-Domain Battle: An Origin Story,” Modern War Institute, 27
October 2017, accessed 16 November 2017, https://mwi.usma.edu/road-multi-domain-battle-origin-story.
6
US Army, Multi-Domain Battle: Evolution of Combined Arms for the 21st Century (Fort Eustis,
VA: US Army Training and Doctrine Command, 2017), 1.
7
Ibid., 2-3; McCoy, https://mwi.usma.edu/road-multi-domain-battle-origin-story.
8
Multi-Domain Battle, 4.
2
The concept currently remains developmental with version 1.0 just released in December
2017. Its eventual character and utility is the subject of ongoing debate in various online forums
and military professional journals. Despite its early stage of development, elements of the concept
are already beginning to appear in core US Army doctrine, for example, the 2017 version of FM
3-0: Operations. 9 Further exploration of the concept is the focus of several major Army and joint
force exercises in 2018 and 2019, notably US Army Training and Doctrine Command’s
(TRADOC) Unified Quest 18, US Army Europe’s (USAREUR) Swift Response and United
States Pacific Command’s (PACOM) Rim of the Pacific (RIMPAC). 10
The Problem
The recently-released 2018 National Defense Strategy declares that “we are emerging
from a period of strategic atrophy” into a world where “Inter-state strategic competition, not
terrorism, is now the primary concern in US national security.” 11 The strategy specifically
identifies two primary peer competitors who have emerged as threats to the established world
order; Russia, and China. The revisionist Russia depicted in the strategy, while cleverly
exploiting new methods and technologies to pursue its strategic aims, does so within a familiar
and established context where the United States can draw upon a wealth of its own and partners
recent experience.
9
US Army, Field Manual (FM) 3-0, Operations (Washington, DC: Department of the Army,
October 2017), 1-77.
10
Megan Eckstein, "Army Set to Sink Ship in 2018 as PACOM Operationalizes Multi-Domain
Battle Concept," USNI.org, May 30, 2017, 3, accessed 11 December 2017,
https://news.usni.org/2017/05/30/pacom-integrating-multi-domain-battle-into-exercises-ahead-of-2018-
rimpac-army-sinkex; Tom Greenwood and Jim Greer, "Experimentation: The Road to Discovery,"
Thestrategybridge.org, March 01, 2018, accessed 03 March 2018, https://thestrategybridge.org/the-
bridge/2018/3/1/experimentation-the-road-to-discovery.
11
US Department of Defense, Summary of the 2018 National Defense Strategy of The United
States of America: Sharpening the American Military’s Competitive Edge (Washington, DC: OSD, 2018),
1.
3
In marked contrast, when the United States “pivoted” back toward the Pacific region in
2012, it was to a region where the US military had not faced a peer enemy in major combat
operations since 1953. The strategic dilemma presented by China’s rise is historically familiar,
that of the established power confronted by a rising regional challenger. However, China’s
military strategy leverages advancements in sensors and long-range strike capability to deny
critical access and basing. This strategy, in concert with the immutable geography of the Pacific
Ocean, threatens to prevent the United States from projecting expeditionary combat power into
the region. The neutralization of US military power, the keystone of our economic and diplomatic
influence in the region, leaves our allies and partners susceptible to ongoing Chinese diplomatic,
informational, and economic pressure. If competing strategically in the region with China is a
principal priority of our national defense than we must re-learn how to fight in the Pacific. 12
The US Army has historically assumed a supporting role in the Indo-Asia Pacific, which
since the conclusion of World War 2 has been largely a maritime and air realm. This status is
exemplified by the default nomination of a Navy Admiral as the Commander of United States
Pacific Command since its creation in 1947. Since the Obama administration’s pivot to the
Pacific in 2012, the Army has struggled to discern new roles for its land forces in contemporary
and future Pacific conflicts. Early efforts like Regional Alignment of Forces (RAF) and US Army
Pacific’s (USARPAC) Pacific Pathways program focused on building individual regional
familiarity and identifying and overcoming the logistical challenges of deploying personnel and
equipment to support recurring security cooperation exercises in the theater.13 However,
deploying and employing land combat forces collectively in the region successfully will be much
more complex than these efforts, or our recent experiences elsewhere suggest.
12
National Defense Strategy of The United States, 4.
13
AUSA, “The U.S. Army in Motion in the Pacific,” April 6, 2015, 2, accessed 20 January 2017,
https://www.ausa.org/publications/us-army-motion-pacific.
4
In light of the current doctrinal thrust toward Multi-Domain Battle, Admiral Harry Harris,
the PACOM Commander, envisioned how a multi-domain approach could be employed in the
Indo-Asia Pacific in his April 2017 testimony before the House Armed Services Committee
(HASC). Harris described “ground, space, electromagnetic spectrum, and cyber forces operating
across archipelagic regions to augment sea and air forces to create temporal pockets of dominance
that can be exploited to gain a tactical and operational advantage.” 14 Thus far, in accordance with
Harris’s vision, US Army MDB efforts in the Indo-Asia Pacific have concentrated on re-
packaging existing land-based Army missile and artillery systems to deliver “cross-domain fires”
against enemy ships. 15 The Army hopes to validate the concept during the summer 2018 Rim of
the Pacific (RIMPAC) exercise by sinking a ship, dubbed a “SINKEX.” 16 To coordinate and
employ these capabilities, as well as to provide air, cyber, and space effects to the joint force, the
Army is developing an experimental Multi-Domain Task Force (MDTF). The MDTF will be a
1500-soldier organization which will be more agile and self-contained than the 4,000-soldier
Brigade Combat Teams (BCT’s) which are the modular building blocks of the current force.
While providing capabilities and effects across domains in support of the joint force is an
important element of Multi-Domain Battle, this narrow focus denies the near-certainty that the
land domain itself is, as General Perkins noted, likely to be just as heavily contested and will need
to be physically occupied before Army cross-domain forces are emplaced there. This task is
likely to fall to Army or Marine Corps land forces who have, thus far, received limited
14
United States Pacific Command Posture, 115th Cong., 19 (2017) (testimony of Admiral Harry
B. Harris Jr.), accessed 02 November 2017, https://www.armed services.senate.gov/imo/media/doc/
Harris_04-27-17.pdf
15
Adm. Harry Harris, "The View from the Indo-Asia-Pacific" (speech, WEST 2017 Conference,
San Diego Convention Center, San Diego, February 21, 2017), accessed 22 October 2017,
http://www.pacom.mil/Media/Speeches-Testimony/Article/1089966/afcea-west-2017-keynote-the-view-
from-the-indo-asia-pacific/
16
Eckstein, accessed 11 December 2017, https://news.usni.org/2017/05/30/pacom-integrating-
multi-domain-battle-into-exercises-ahead-of-2018-rimpac-army-sinkex.
5
consideration in the development of the Multi-Domain Battle Concept. It is toward examining
how these forces have fought successfully in the past and informing how they should be
employed in the near-future that this study is directed.
The Research Question

The United States Army’s mission remains “to fight and win our Nation’s wars by
providing prompt, sustained land dominance across the full range of military operations and
spectrum of conflict in support of combatant commanders.” 17 How then should the Army employ
its land combat forces, informed by the Multi-Domain Battle Concept, to fight and win future
conflicts in the Indo-Asia Pacific region?
Secondary Questions
To answer the primary research question, it is also necessary to consider these secondary
questions:
1. Using historical case study methodology, what campaigns can we examine from recent
US Army land combat in the Indo-Asia Pacific which approximate the conditions expected in the
Multi-Domain Battle environment?
2. What will a future Multi-Domain Battle campaign in the Indo-Asia Pacific against a
near-peer enemy look like?
3. What elements of a Multi-Domain Battle approach have been employed before in the
Indo-Asia Pacific; and what lessons can we derive from them to inform the further development
of Multi-Domain Battle?
17
US Army, "Mission," www.army.mil, September 18, 2017, accessed 05 November 2017,
https://www.army.mil/info/organization/.
6
Assumptions
This thesis and its recommendations necessarily assume the continuing validity of the
following assumptions:
1. The United States will desire to maintain the position of regional leadership it has
enjoyed in the Indo-Asia Pacific since the conclusion of World War 2.
2. The United States will continue to routinely pursue its political ends using military
means. There will be no drastic ideological shift away from military force.
3. Both the United States and its likely adversaries in the Indo-Asia Pacific will continue
to choose to contest militarily at least partially in the land domain. Conceptual or doctrinal trends
which favor other domains will not obsolete land power.
4. The presence of humans will remain “the distinguishing characteristic of the land
domain.” 18 Potential US or adversary technological developments in robotics or artificial
intelligence will not obviate this fact in the near-future (2020-2035). 19
5. The United States will continue to maintain a distinct, organized Army to “fight and
win the Nation’s wars through prompt and sustained land combat.” 20 Prompt is interpreted as
“required to provide combat-ready forces immediately.” 21
If all these assumptions are correct, how best can the United States Army visualize the
role of land power in Multi-Domain Battle in the near-future Indo-Asia Pacific?
18
US Army, Army Doctrine Publication (ADP) 1, The Army (Washington, DC: Department of the
Army, September 2012), 1-1.
19
Elsa B. Kania, "Artificial Intelligence and Chinese Power," Foreign Affairs, December 15,
2017, accessed 05 March 2018, https://www.foreignaffairs.com/articles/china/2017-12-05/artificial-
intelligence-and-chinese-power.
20
The Army, 1-8.
21
Ibid.
7
Operation ICEBERG: Proto-Multi-Domain Battle in the Indo-Asia Pacific
Perhaps the most appropriate historical example to inform Multi-Domain Battle in the
Indo-Asia Pacific region is Operation ICEBERG, the April 1945 campaign to invade the
Japanese-held Ryukyu Islands, notably Okinawa. Operation ICEBERG is considered “the
culmination of the experience of all previous operations in the Pacific war.”22 As such, it was
planned as the penultimate step in the allied “Island-Hopping” strategy to successively isolate and
invade the Japanese home islands and embodied “the lessons learned in the long course of the
battle against the Japanese outposts in the Pacific.” 23 Chief amongst these were the lessons of
“cooperation and combined striking power of the services.” 24 To prevent the parochial
distractions which had plagued earlier island campaigns in the Pacific, Operation ICEBERG was
deliberately planned and directed by a multi-service precursor to the modern Joint Task Force
(JTF) structure, the Central Pacific Task Forces under the command of Admiral Raymond
Spruance. 25 US Army Lieutenant General Simon Bolivar Buckner, commander of the
expeditionary troops, understood the opportunities of the organically-joint nature of his
organization, and sought to enable it by incorporating Navy and Marine Corps officers throughout
his staff. 26 His approach produced an example of convergence, recently introduced as an essential
component of Multi-Domain Battle.
As the final major offensive campaign of World War 2, Operation ICEBERG was also
the last American expeditionary amphibious assault of an island conducted in the Indo-Asia
22
Roy Edgar Appleman et al., Okinawa: The Last Battle (Washington, DC: Center of Military
History, US Army, 2005)., 17.
23
Ibid., 17.
24
Ibid., 23.
25
Ibid., 22.
26
Ibid., 27.
8
Pacific region. A still-capable peer enemy attempted to deny and then contest American access in
all three existing domains; sea, air, and land. It was only through a systematic and coordinated
integration of capabilities in and across domains that the United States was able to negate these
efforts by the Japanese forces holding the Ryukyus. Because of these similarities in environment
and approach, a historical analysis of the campaign can provide insights to assist Army and joint
forces preparing to execute similar operations under future conditions.
Scope and Limitations and Delimitations

The scope of this investigation is defined geographically by the Indo-Asia Pacific region,
today the PACOM area of responsibility. The study will temporally encompass and compares two
periods. The historical case study examines the years of American conflict in the Pacific Theater
during World War 2 from 1944 to 1945. The period of comparison is the period of near-future
conflict posited in the Multi-Domain Battle Concept, 2025-2040. 27
This investigation is limited by the technological inaccessibility of two of the five
domains incorporated into the Multi-Domain Battle Concept, space and cyberspace. It is limited
to existing primary sources. It is also limited by the developmental nature of the Multi-Domain
Battle Concept and the inability to predict the conditions of a future operating environment with
absolute clarity.
This investigation is deliberately delimited by excluding discussion of a future conflict on
the Korean Peninsula from the comparison as it presents distinctly different environmental
conditions and challenges from those generally present throughout the rest of the Indo-Asia
Pacific. As such, it also avoids contrasting the character of World War 2 amphibious operations
in the Pacific with the more recent, but considerably smaller examples executed during the
Korean War. The investigation relies exclusively upon the case study of Operation ICEBERG
27
9
because it represents the final maturation of joint forcible entry theory and practice evolved
during the Pacific Theater “Island Hopping” campaign and is thus assumed to incorporate prior
advances. It also represents the most recent US operation of this type and the largest in scale ever
undertaken.
10
Multi-Domain Battle
Introduction
Multi-Domain Battle: The Evolution of Combined Arms for the 21st Century is an
emerging operational concept developed by the United States Army, with the cooperation of the
United States Marine Corps and Air Force, which describes how Army forces will compete with,
and when necessary, defeat peer adversaries in the near future (2025-2050). 28 The inspiration for
Multi-Domain Battle lies in Deputy Defense Secretary Robert Work’s April 2015 speech at the
Army War College Strategy Conference which discussed the changing character of warfare
brought about by the diffusion of precision-guided munitions, advanced sensors, and
“informationalized” warfare techniques. 29 The conditions of Work’s future operating
environment mirror the operational context of the Multi-Domain Battle Concept; characterized by
all the domains being contested, increased lethality and complexity throughout the operational
area, and challenged deterrence and deployment of US forces. 30
Work offered elements of a possible solution, which he termed “AirLand Battle 2.0” and
challenged the Army to further develop and refine his concept, in his words to “figure it out.” 31
The Army’s Training and Doctrine Command (TRADOC) looked to three sources of inspiration
to address these challenges; the Capstone Concept for Joint Operations (CCJO), the Army
Operating Concept (AOC), and the Marine Corps Operating Concept (MOC). 32 The CCJO
28
29
McCoy, https://mwi.usma.edu/road-multi-domain-battle-origin-story; Bob Work, "Deputy
Secretary of Defense Speech" (speech, Army War College Strategy Conference, US Army War College,
Carlisle, PA, April 8, 2015), April 8, 2015, accessed 05 March 2018,
https://www.defense.gov/News/Speeches/Speech-View/Article/606661/army-war-college-strategy-
conference/.
30
Multi-Domain Battle., 4-6.
31
Work, "Deputy Secretary of Defense Speech"
32
McCoy, “The Road to Multi-Domain Battle: An Origin Story”
11
establishes the necessity for achieving cross-domain synergy. The AOC specifies that the Army
should see itself as a contributor to the joint force. The MOC highlights the danger of enemy
operations prior to and below the level of open conflict. The resultant white paper, Multi-Domain
Battle: Combined Arms for the 21st Century, was released in February 2017.
In light of these imminent changes in the character of warfare, the Multi-Domain Battle
Concept defines a central military problem that must be solved; “How will Army forces, as part
of the Joint Force and with partners, deter and defeat increasingly capable peer adversaries intent
on fracturing allied and Joint Force cohesion in competition and armed conflict?” 33 It answers
this problem by proposing a central idea, and several components which together comprise the
underlying theory of Multi-Domain Battle:
“Army forces, as part of the Joint Force, conduct Multi-Domain Battle to deter and defeat
increasingly capable adversaries in competition, armed conflict, and a return to
competition by calibrating force posture; by employing resilient, cross-domain capable
formations that can maneuver on the expanded battlespace; and by converging
capabilities across multiple domains, environments, and functions to create windows of
advantage that enable maneuver. 34
This central idea highlights the numerous elements which the Army is attempting to
incorporate into the Multi-Domain Battle Concept. These elements are competition vs. armed
conflict, an expanded battlespace visualized in a new operational framework, calibrating force
posture, employing resilient formations, and converging capabilities. 35
Competition vs. Armed Conflict

Multi-Domain Battle proposes an enhanced understanding of the spectrum of conflict in
which opposed actors exist in a state of continuous, ongoing competition, transition to armed
conflict to achieve their discrete strategic objectives, and then return to competition. During
33
34
Ibid.
35
Ibid., 2-4.
12
competition, adversaries seek to achieve their strategic objectives without escalation or to posture
their forces to support escalation should it become desirable or necessary. Adversaries may
employ reconnaissance, unconventional warfare, information warfare, or conventional forces.
The Joint Force and its partners seek to counter these actions by proactively stabilizing while
opposing destabilization campaigns, deterring escalation, and preparing to defeat adversaries
should they transition to armed conflict.
If an adversary chooses to escalate to armed conflict, the Joint Force and its partners seek
to prevent them from achieving a fait accompli, a thing accomplished and presumably
irreversible, at the outset.36 They do this by conducting counter-reconnaissance, reconnaissance,
and operational preparation of the environment; contesting the enemy immediately in all
domains; disrupting the enemy’s main effort or attack, and deploying forces rapidly to defeat the
enemy and achieve a desirable outcome. 37 The goal of armed conflict is to set conditions for a
negotiated outcome which enables the Joint Force and its partners to return to competition on
favorable terms.
At the conclusion of a Multi-Domain Battle campaign, the Joint Force and its still-
capable adversary return to competition, but with the Joint Force retaining the initiative to
consolidate a “sustainable position of relative advantage.” 38 The adversary remains capable of
pursuing its objectives through subversion and other methods short of armed conflict but is
deterred from re-engaging in open hostilities and is prevented from achieving its objectives or
further destabilizing the regional security environment.
36
37
Ibid., 22.
38
Ibid.
13
The Expanded Battlespace
The second major element of Multi-Domain Battle is the introduction of an expanded
physical battlespace. This expanded battlespace is necessitated by both the Joint Force and its
peer adversaries’ ability to contest and deny all domains at extended distances. This expanded
battlespace is captured and visualized in the Multi-Domain Battle Operational Framework.
Figure 1. The Multi-Domain Battle Operational Framework
Source: Multi-Domain Battle: Evolution of Combined Arms for the 21st Century (Fort Eustis,
VA: US Army Training and Doctrine Command, 2017), 9.
The Multi-Domain Battle Operational Framework depicts the possible range of friendly
and enemy activities and capabilities using physical areas within the expanded battlespace. The
Strategic and Operational Deep Fires Areas are areas which, due to distance or restriction, are
beyond the reach of conventional maneuver forces.39 These areas are the purview of special
39
14
operations forces, joint fires, information operations, or virtual capabilities and effects here are
often transitory. The Deep Maneuver Area is the area where conventional maneuver is possible
but requires support from multi-domain capabilities to access, enable, and sustain. In a typical
campaign, many of the operational objectives would lie in the Deep Maneuver Area. Effects here
are more persistent but still require significant enabling support. The Close Area is where friendly
and enemy forces physically meet and “contest for control of physical space in support of
campaign objectives.” 40 The Support Areas - Tactical, Operational, and Strategic - represent the
areas where various capabilities that support the Joint Force reside. Due to the increasing range of
both enemy and friendly capabilities, all levels of the support area are at risk of attack, even if
only from cyberspace or information operations.
Calibrate Force Posture:

The first component of Multi-Domain Battle is force posture. Force posture is “the
positioning of capabilities to achieve a purpose.” 41 In Multi-Domain Battle, forward presence
forces and partner forces are arrayed during competition to counter adversary activities and
prevent potential fait accompli campaigns from succeeding. In the event of an escalation to armed
conflict, these forces will contest the enemies’ A2/AD efforts. They will be reinforced as rapidly
as possible by expeditionary forces capable of maneuvering directly from the homeland, or from
elsewhere within the theater.
Employ Resilient Formations:

The second component of Multi-Domain Battle is resilient formations. Resilient
formations “remain effective despite multiple forms of enemy contact and are cross-domain
40
41
Ibid.
15
capable.” 42 They are designed to avoid adversary long-range precision strike assets by
disaggregating and maneuvering semi-independently without secured flanks, lines of
communication, or continuous assured communications with their higher headquarters. 43 They
are capable of cross-domain maneuver, either organically or when supported by other
organizations, and can conduct noncontiguous operations when necessary. 44
Converge Capabilities:
The third component of Multi-Domain Battle is convergence. Convergence is “the
integration of capabilities across domains, environments, and functions in time and physical space
to achieve a purpose.” 45 It is “the act of applying a combination of capabilities (lethal and non-
lethal, whether within a domain or cross-domain) in time and space for a single purpose.” 46 The
convergence of effects or capabilities is the major evolutionary departure from previous additive
concepts like combined arms or joint operations. The goal of convergence is the creation of
Windows of Advantage that “enable the Joint Force to maneuver and achieve objectives, exploit
opportunities, or create dilemmas for the enemy.” 47
Incorporating all these elements, the Multi-Domain Battle Concept offers a proposed
definition of Multi-Domain Battle; the “convergence of capabilities to create windows of
advantage (often temporary) across multiple domains and contested areas throughout the depth of
the battlespace to seize, retain, and exploit the initiative; defeat enemies; and achieve military
objectives.” 48 The following analysis of Operation ICEBERG will adopt this definition.
42
43
Ibid.
44
Ibid.
45
Ibid.
46
Ibid.
47
Ibid., 2.
48
Ibid., 77.
16
Case Study
Operation ICEBERG
Operation ICEBERG, the allied campaign to invade the Ryukyu Islands, began on 3
October 1944 with receipt of Joint Chiefs of Staff (JCS) Directive 713/19 directing Fleet Admiral
Chester Nimitz, Commander in Chief, Pacific Ocean Areas (CinCPOA), to “occupy one or more
positions in the Ryukyu Islands by 1 March 1945.” 49 The specified landing date, L-Day or “Love
Day,” later moved to 1 April 1945. 50 The preparatory convergence of naval and air capabilities to
isolate the Ryukyus and create a window of advantage for the ground invasion commenced on 10
October 1944 and continued through 19 March 1945. 51 Subsidiary landings in the nearby Kerama
Retto and on Keise Shima to establish positions to support the main landing began on 26 March
1945 and were completed on 31 March 1945. 52 The main force landed on Okinawa precisely at its
pre-determined H-Hour, 0830 on 1 April 1945. The period of large-scale land combat lasted 83
days, ending on 22 June 1945 with the ritual suicide of the 32d Army Commander and capture of
his final redoubt on Hill 89. A period of consolidation followed to eliminate remaining resistance
and secure abandoned arms and positions. This period ended on 30 June 1945 and Operation
ICEBERG was declared complete on 2 July 1945.
The Joint Operations Area (JOA)

The Joint Operations Area for Operation ICEBERG encompassed the Ryukyu Islands,
the Nansei Shoto, and their surrounding sea and airspace. The Ryukyus, part of the Japanese
49
Appleman, et al., 4.
U.S. Tenth Army, Report of Operations in Ryukyus Campaign, 26 March 1945 to 30 June 1945,
50
TENTH ARMY ACTION REPORT (Okinawa, JP: HQ, Tenth Army, 1945), 3-0-9.
51
52
Ibid., 51-56.
17
Archipelago, lies between the East China Sea and the Pacific Ocean. Approximately 200 miles to
the north is the southernmost Japanese home island of Kyushu. Approximately 450 miles to the
west is mainland China. 550 miles to the southwest is Formosa, present-day Taiwan. The
Philippine island of Luzon is approximately 650 miles to the south. The JOA lies approximately
6,000 miles from the west coast of the United States and 4,100 miles from the nearest major naval
staging base at Pearl Harbor, Oahu, Hawaii.
Inside the JOA, the approximately 140 Ryukyu Islands form a 790-mile-long archipelago
extending from Kyushu to Taiwan along the tectonic plate boundary where the Philippine Sea
Plate subducts the Eurasian Plate. 53 This feature forces the seafloor above the surface of the ocean
and produces to the characteristic rocky limestone hills pocked with natural caves which are
common throughout the Ryukyus but held special significance for both the defenders and
attackers of Okinawa. The islands have a wet, subtropical climate and are predominately covered
by dense, uniform evergreen broadleaf forest except in areas of extreme elevation or extensive
agricultural activity. 54
At the center of the Ryukyus, at approximately 26° North latitude lies Okinawa Gunto, or
“Okinawa Island Group.” This cluster of approximately fifty islands was the area of operations
(AO) for Task Force (TF) 56, the expeditionary force assigned to execute the decisive operation,
the invasion of Okinawa proper. The AO also encompasses shaping operations in support of the
main landing on the Kerama Islands and Keise Island to the southwest of Okinawa, and Ie Shima
to the northwest.
53
Kazuhiko Fujita et al., Nature in the Ryukyu Archipelago: Coral Reefs, Biodiversity, and the
54
Natural Environment (Nishihara-machi (Okinawa-ken), JP: International Research Hub Project for Climate
Change and Coral Reef/Island Dynamics Faculty of Science, University of the Ryukyus, 2015), 52-54.
18
Okinawa, the largest island, runs northeast to southwest for 67 miles, narrowing in the
middle to two miles from its maximum width of eighteen miles, and having a total land area of
485 square miles. 55 The northern half of the island is sparsely-populated and covered by a dense,
unbroken forest called the Yanbaru. On the northwestern shore, the Motobu Peninsula extends
westward into the East China Sea toward Ie-Shima. To the south, Okinawa narrows to a neck,
then widens at Zampa Point. Extending south from Zampa Point and bisected by the Bishi River
are the Hogushi Beaches, the landing site for the invasion. Finally, in the sparsely-vegetated and
more populated south are the port of Naha, the largest city, and Shuri, the ancient capital of the
Ryukyu Kingdom. This southern area is where the major land battles were fought between the
defending Imperial Japanese Army (IJA) 32d Army and the ground combat elements of TF 56
organized around the Tenth US Army.
55
Appleman, et al., 7-8.
19
Figure 2. The Island of Okinawa
Source: Okinawa: The Last Battle (Washington, DC: US Army Center of Military History, 2005),
MAP NO. II.
20
The Belligerents
The Japanese 32d Army was activated at Naha on 1 April 1944 by Lieutenant General
Masao Watanabe to consolidate the existing garrison forces on Okinawa and to plan and lead the
defense of the island. In August 1944, Lieutenant General Mitsuru Ushijima replaced Watanabe.
Ushijima brought an entirely new staff and led the 32d Army until its defeat and his suicide in
June 1945.
Three distinct units compromised 32d Army. The 24th Division, a triangular division,
was organized for combined-arms maneuver against the modern, mechanized Soviet Army
shortly after the Nomonhon incident. 24th Division’s strength prior to the invasion was 14,360. 56
The 62d Division was a pentagonal light division organized for counterinsurgency in China. 62d
Division’s strength prior to the invasion was 11,623. 57 The 44th Independent Mixed Brigade
(IMB) united two independent regiments, the 2nd and 15th. 44th IMB’s strength prior to the
invasion was 4,485. 58 There was also a centralized artillery command and the 27th Tank
Regiment with fourteen medium tanks and thirteen light tanks. 59 Altogether 32d Army contained
about 67,000 IJA personnel. It also controlled 9,000 Imperial Japanese Navy personnel, mainly
construction and Naval Base Force personnel, and as many as 24,000 mobilized native
Okinawans or Boetai with varying degrees of loyalty. 60
56
Thomas M. Huber, Japan's Battle of Okinawa: April-June 1945, vol. 18, Leavenworth Papers
(Fort Leavenworth, KS: Combat Studies Institute Press, 1990), 14-19.
57
Ibid.
58
Ibid.
59
Ibid., 19.
60
Ibid.
21
Figure 3. Japanese Thirty Second Army Defensive Dispositions, 1 April 1945
Source: US Military Academy, West Point, Department of History, accessed 09 April 2018,
https://www.westpoint.edu/history/SiteAssets/SitePages/World%20War%20II%20Pacific/
ww2%20asia%20map%2048.jpg.
To prevent the US Navy and Army Air Forces (AAF) from supporting a landing, the
Japanese formulated a comprehensive A2/AD plan to contest the air and maritime domains. An
invasion of the Ryukyus would be met by a swarm of 1,500 land-based aircraft originating from
22
Kyushu, Formosa, and the Chinese mainland. 61 These consisted of a mix of conventional aircraft
and those of the IJN “Special Attack Units,” the infamous Kamikaze suicide aircraft. They were
to be augmented with an additional 300 suicide aircraft under 32d Army on Okinawa itself,
though these never materialized. 62 The IJN also based seven Sea Raiding Squadrons in the
neighboring Kerama island group. These maritime analogs to the Kamikaze pilots crewed small
wooden speedboats rigged with depth charges whose purpose was to attack enemy ships as they
attempted to put their troops and cargo ashore. 63 IJHQ believed that these combined air and sea
attacks would be sufficient to effectively defeat the US landing force, leaving the 32d Army
responsible for securing the facilities on the island and destroying any remnants that managed to
effect a landing with their mobile reserve force. 64
The principal allied belligerent in Operation ICEBERG was the Central Pacific Task
Forces, a predecessor to the modern joint task force construct, commanded by Admiral Raymond
Spruance. Admiral Spruance maintained direct control of the two carrier task forces assigned to
the Ryukyus operation, TF 58, the US Fast Carrier Force, and TF 57, the British Carrier Force.
These forces contained sixteen and ten carriers respectively, as well as numerous battleships,
cruisers, and supporting vessels. 65 The carrier forces were responsible for preventing Japanese
maritime and air interference against the amphibious force (AF) as it entered the JOA, protecting
the landing, and neutralizing enemy defensive positions before and during the landing.
61
Huber, 4.
62
Ibid., 25.
63
64
Huber, 4.
65
Appleman, et al., 49, 97.
23
Figure 4. Organization of Central Pacific Task Force
Source: III MEF Staff Ride Battle Book: Battle of Okinawa (Quantico, VI: US Marine Corps
History Division, 2015).
The designated amphibious task force (ATF), the “Navy task organization formed to
conduct amphibious operations,” was TF 51, coined the “Joint Expeditionary Force.” 66 TF 51,
commanded by Vice Admiral Richmond K. Turner, was responsible for securing and developing
positions in the Ryukyu group. Modern joint amphibious operations doctrine would describe
Turner as commander, amphibious task force, or “CATF.” 67 At Turner’s disposal were Army,
Navy, and Marine Corps forces organized into five subordinate task forces and two groups. In an
improvement upon previous amphibious operations in the “island-hopping” campaign, Spruance
designated that Turner’s command would last only through the amphibious phase of the
66
Joint Chiefs of Staff, Joint Publication (JP) 3-02, Amphibious Operations (Washington, DC:
Joint Chiefs of Staff, July 2014), GL-7.
67
Ibid., GL-10.
24
operation, thereafter shifting to the commander of the landing force (CLF), Lieutenant General
(LTG) Simon Bolivar Buckner, Jr. 68
Figure 5. Organization of Expeditionary Troops for the Ryukyus Campaign, January 1945
CHART III.
General Buckner commanded TF 56, the expeditionary “Landing Force” for Operation
ICEBERG. TF 56 was organized around a pre-existing field army, the US Tenth Army, which
was originally established for Operation CAUSEWAY, the superseded attack to seize Formosa.
For Operation ICEBERG, Tenth Army contained dedicated Navy and AAF elements, an Island
Command to garrison and administer Okinawa, and two landing forces organized around the
Army XXIV Corps in southern Okinawa and the Marine III Amphibious Corps in the north. Each
corps contained two reinforced divisions. There were also separate Western Island and
Demonstration forces, and floating and area reserves.
68
Amphibious Operations, GL-10; Appleman, et al., 23.
25
Outside of the forces allocated to the Central Pacific Task Forces, an extensive bombing
effort conducted primarily by the land-based heavy bombers of the United States Army Air
Forces preceded and supported Operation ICEBERG. Initial control of the air and sea having
been determined to be essential for the subsequent landings, B-29 Superfortresses of the XX and
XXI Bomber Commands based in India and the Mariana Islands struck military targets on
Formosa, Kyushu, and Okinawa itself prior to L-day. 69 These were augmented by diverting
aircraft supporting the capture of Luzon to attack targets on Formosa and utilizing the Fourteenth
Air Force in mainland China to conduct search and rescue and attack targets in Hong Kong. 70 All
told, Admiral Spruance’s assigned and supporting forces represented “the greatest concentration
of land, sea, and air forces ever used in the Pacific.” 71
Immediate Military Objectives of Operation ICEBERG

The Joint War Plans Committee (JWPC) “Plan for the Seizure of the Ryukyus” directed
five military objectives for Operation ICEBERG; establishment of airfields, establishment of
advanced naval anchorages, tightening of the sea and air blockade of Japan, acquisition of bases
permitting amphibious assaults against Kyushu and Japanese possessions in China, and the denial
of the islands to the Japanese. 72
Planning and Preparation; 10 August 1944 to 10 October 1944

Planning for Operation ICEBERG began in 1944 with a different military objective; seize
the Japanese-held island of Formosa, present-day Taiwan. The 1943 SEXTANT conference in
Cairo, attended by US President Franklin Roosevelt, British Prime Minister Winston Churchill,
69
Report of Operations in Ryukyus Campaign, 7-1-3; Appleman, et al., 21.
70
71
Ibid., 19.
72
Joint War Plans Committee (JWPC), Plan for Seizure of the Ryukyus, (Washington, DC: Joint
War Plans Committee, 1944), 20.
26
and Republic of China Chairman Chiang Kai-shek, agreed upon a strategy for the eventual
isolation and bombardment of the Japanese home islands. The strategy directed a series of
amphibious attacks to seize key island positions along two general axes; General Douglas
MacArthur’s South West Pacific Area (SWPA) forces would advance along the New Guinea-
Philippine axis, and Admiral Chester Nimitz’s Pacific Ocean Area (POA) forces would advance
through and capture the Mandated Islands. These converging attacks aimed to progressively
isolate and provide a base for major amphibious assaults to seize key terrain in the Formosa-
Luzon-China area in spring 1945. Once secured, the bases would enable the allies to blockade,
bomb, and if necessary, invade Japan. 73
On 10 August 1944, Nimitz directed his task force commanders; Spruance, Turner, and
Buckner, to plan and execute Operation CAUSEWAY, the invasion of Formosa. 74 However,
invading Formosa proved controversial and a projected shortfall in forces available prior to
defeating Germany resulted in a reevaluation of strategic objectives and the indefinite
postponement of Operation CAUSEWAY on 3 October 1944. 75 In its place, the Joint Chiefs of
Staff concurred with a recommendation by Admiral Ernest King, the Commander in Chief,
United States Fleet (COMINCH) to redirect MacArthur to seize Luzon in December 1944; then
Nimitz would seize Iwo Jima in January 1945, and invade the Ryukyus on 1 March 1945. 76
Nimitz notified his staff of their new mission on 5 October 1944.
73
Minutes of the Sextant Conference, November-December 1943, 255, Accessed April 11, 2018.
http://cgsc.contentdm.oclc.org/cd m/ref/collection/p4013coll8/id/3691
74
Benis M. Frank and Henry I. Shaw, Jr., Victory and Occupation, vol. 5, History of U.S. Marine
Corps Operations in World War 2 (Washington, DC: Headquarters, US Marine Corps, 1968), 6.
Ibid., 12; Richard Zee, “Operational Perspectives of the Okinawa Campaign (Operation
75
ICEBERG)” (research paper, Newport, RI: US Naval War College, Operations Department, 1994), 10-11.
76
Benis M. Frank and Henry I. Shaw, Jr., Victory and Occupation, 13.
27
Tenth Army’s planning for Operation ICEBERG began when they received advance
notification of the change in objective from CINCPOA on 9 October 1944. A formal directive
designating LTG Buckner as the commander of TF 56, the expeditionary troops, arrived the next
day. 77 Another directive from CINCPOA on 25 October 1944 provided further planning
guidance. CINCPOA’s immediate task was to “capture, occupy, defend, and develop Okinawa
Island and establish control of the sea and air in the Nansi Shoto area” and to eventually “extend
control of the Nansei Shoto by capturing, occupying, defending, and developing additional
positions.” 78 The purpose was to establish bases from which to:
(1) Attack the main islands of JAPAN and their sea approaches with naval and air
forces.
(2) Support further operations in the regions bordering on the EAST CHINA SEA.
(3) Sever Japanese sea and air communications between the EMPIRE and the mainland
of ASIA, FORMOSA, MALAYA, and the NETHERLANDS EAST INDIES.
(4) To establish secure sea and air communications through the EAST CHINA SEA to
the coast of CHINA and the YANGTZE VALLEY.
(5) To maintain unremitting military pressure against JAPAN.79
From this information, Tenth Army derived its mission:
The Tenth Army, as Expeditionary Troops, initially under the command of the
Commander Joint Expeditionary Force, will assist in the capture, occupation, defense,
and development of OKINAWA ISLAND and establishment of control of the sea and air
in the NANSEI SHOTO (RYUKYU) Area; with the eventual aim of extending control of
the NANSEI SHOTO by capturing, defending, and developing additional positions. 80
77
Report of Operations in Ryukyus Campaign, 3-0-1.
78
Commander in Chief, U.S. Pacific Fleet and Pacific Ocean Areas, Joint Staff Study: ICEBERG
(Pearl Harbor, HI: HQ, US Pacific Fleet, 1944), 2.
79
Ibid.
80
28
The amphibious invasion, preceded by an extensive naval and air campaign to isolate and
prepare the JOA would occur in three phases. 81 Phase I, beginning six days before the main
landings, entailed subsidiary landings on the adjacent islands of the Kerama Retto and Keise.
These landings would eliminate land-based artillery batteries and a suspected Japanese naval
base, establish a protected anchorage and seaplane base for the Navy, and emplace Army long-
range artillery to support the main landing. Phase I concluded with the main landings on the
western Hagushi beaches and a diversionary feint in the south on L-day. Phase II directed the
seizure of Ie Shima and the occupation of northern Okinawa. Phase III directed the seizure of
several adjacent islands. In execution, Japanese ceding of the landing area and much of the
northern portion of Okinawa resulted in unanticipated success during Phase I and early
accomplishment or cancellation of most the Phase II and Phase III objectives.
On 25 October 1944 Tenth Army received notification of the forces allocated to it for
Operation ICEBERG. 82 Tenth Army received assigned two corps; an Army corps, the XXIV
Corps, consisting of the 7th, 77th, and 96th Infantry Divisions, and a Marine Amphibious Corps,
the III Amphibious Corps, consisting of the 1st, 2d, and 6th Marine Infantry Divisions. The 27th
Infantry Division and an additional unnamed Army division would act as an area reserve.
Simultaneously, the Tenth Army staff conducted a bottom-up analysis of the troops required to
execute their preferred version of the invasion plan, known as “Plan Fox.” The requirements they
generated contained a substantial increase in non-divisional support and logistics troops, some
70,000 more than envisioned by the Joint Staff Study. 83 This discrepancy was resolved in a series
of conferences examining ongoing operations in the Pacific theater to prioritize the available
81
82
Ibid., 3-0-8.
83
Ibid.
29
forces for future operations. The conferences produced a finalized task organization which
satisfied most of Tenth Army’s requirements.
The allocated forces presented a challenge with regards to force posture; they were
scattered throughout the Pacific, in most cases at the division and below level. The III Marine
Amphibious Corps had divisions on the Russell Islands, Saipan, and Guadalcanal. The XXIV
Corps with its subordinate divisions, the 7th, 77th, and 96th Infantry Divisions, was engaged in
active combat in Leyte until February 1945. 84 The 27th Infantry Division, the floating reserve,
was at Espiritu Santo recovering from the Battle of Saipan the previous summer. Tenth Army
Headquarters and staff, along with much of its support and naval augmentation was located at or
passing through Oahu. 85
Preliminary Operations; 10 October 1944 to 31 March 1945

Preliminary operations to “inflict heavy losses upon Japanese air forces and reduce the
potential threat to our expeditionary forces” commenced on 10 October 1944. The Navy Fast
Carrier Task Force composed of nine carriers, five battleships, and dozens of support ships struck
the port of Naha, and major airbases and naval support facilities throughout the Ryukyus. 86 They
also photographed the islands. 1,356 carrier airstrikes destroyed 111 aircraft, sunk at least 70
various naval vessels, and destroyed 80 percent of Naha, the capital city of Okinawa Prefecture. 87
The Fast Carrier Task Force returned twice more in January 1945; first on 3 January to
destroy enemy aircraft and bases in Formosa, and again on 22 January to photograph areas of
interest for the invasion. Both raids also targeted naval, ground, and air facilities. 88
84
85
Ibid., 5-0-8.
86
Joint Staff Study: ICEBERG, 2.
87
Appleman, et al., 44-45; Joint Staff Study: ICEBERG, 3.
88
30
During February 1945 the Fast Carrier Task Force, now designated TF 58, supported
Admiral Nimitz’s amphibious invasion of Iwo Jima, Operation DETACHMENT. TF 58 struck
targets in the Tokyo area on 16 February and 25 February 1945. On their return they again
attacked targets throughout the Ryukyus, sinking more than 50 ships, and destroying 41 aircraft.
Also, during this time, Navy and Army search and patrol aircraft, and Navy submarines
interdicted the sea lines of communication between the Japanese home islands and the Ryukyus
resulting in the effective isolation of the Ryukyus from Formosa and mainland Japan by mid-
February. 89
Finally, TF 58 visited the southern home islands a final time on 14 March 1945 with
sixteen carriers, eight battleships, and sixteen cruisers; this time to neutralize naval and air bases
on Kyushu, Shikoku, and Honshu. American aircraft savaged the airbases on 17 and 18 March,
shooting down 102 Japanese aircraft and destroying an additional 275 on the ground. However,
the Japanese aircraft responded on 18 March, damaging the carriers Yorktown and Enterprise. TF
58 shifted its focus to warships and facilities on 19 March 1945. The attacks damaged the
battleship Yamato and an escort carrier, as well as sinking some merchant shipping. Japanese
aircraft again counterattacked, damaging the carriers Franklin, Wasp, and Intrepid. The task force
withdrew, covered by a final attack against air bases and aircraft. The strikes on 19 March cost
the Japanese an additional 322 aircraft damaged or destroyed. Japanese aircraft pursued TF 58
south, launching ineffective attacks on 20 March and 21 March. Finally, on 22 March 1945, the
task force rendezvoused with its resupply ships, reorganized, and prepared to bombard targets on
Okinawa to cover the approach of the Joint Expeditionary Force, TF 51. 90
89
Victory and Occupation, 37; Appleman, et al., 46.
90
Charles Sidney Nichols, Jr. and Henry I. Shaw, Jr., Okinawa: Victory in the Pacific
(Washington, DC: Headquarters, US Marine Corps, 1955), 37-38; Appleman, et al., 49-50; Joint Staff
Study: ICEBERG, 3.
31
Also, in March, land-based United States Army Air Force (USAAF) bombers from
outside the Pacific Ocean Areas supported the isolation and preparation of the Ryukyus. 20th
Bomber Command B-29’s operating from China struck from 1 March to 16 March, while 21st
Bomber Command B-29’s operating from the Marianas attacked Okinawa and then shifted their
attacks to Kyushu. 91 Aircraft from the Fourteenth Air Force in China struck Hong Kong, and the
Southwest Pacific Air Forces conducted searches and attacked Formosa. 92
While other forces prepared the JOA, Tenth Army began loading and embarking its
forces. Shipping was divided into two categories; Assault shipping for expeditionary troops and
equipment, and Garrison shipping for garrison troops and remaining expeditionary troops. 93 The
Tenth Army commander was responsible for overseeing the assault shipping, though subordinate
corps and division commanders supervised the embarkation of their respective elements, guided
by the Transport Quartermaster Teams and the Navy Transport Squadron (TransRon)
commanders. 94 Each division was allocated a TransRon of fifteen amphibious transports (APA’s)
and six attack cargo ships (AKA’s) with associated landing ship, tanks (LST’s) and landing ship
mediums (LSM’s). 95 The mounting points for III Amphibious Corps were at the Russell Islands,
Saipan, and Guadalcanal, while XXIV Corps mounted at Leyte. 96 The headquarters and support
units mounted at Oahu. 97 The first assault troops, 77th Infantry Division Battalion Landing Teams
91
Report of Operations in Ryukyus Campaign, 7-I-3.
92
Ibid.; Appleman, et al., 21.
93
94
Appleman, et al., 41; Report of Operations in Ryukyus Campaign, 5-0-1.
95
96
97
Ibid.
32
(BLT’s) tasked to secure positions in the Kerama Retto, began their movement northeast by north
on 18 March 1945. 98
As the invasion flotilla approached, TF 58 positioned themselves to the north and east of
Okinawa to isolate the Ryukyus and cover the Joint Expeditionary Force. They were soon joined
by the arriving Amphibious Support Force, TF 52, responsible for assisting in the isolation,
minesweeping, underwater demolition, and air and naval preparation of Okinawa. 99 TF 52
initiated its naval bombardment of Okinawa on 25 March 1945, first at long range, then
incrementally closer as the mine clearance progressed until finally reaching its optimum
effectiveness on 30 March. 100 At the same time, TF 58 initiated air attacks against Okinawan
targets, prioritizing enemy aircraft and suicide boats. They destroyed 80 enemy aircraft on the
ground, as well as sinking several small enemy craft and demolishing eight submarine pens. 101
Concurrently, the British Carrier Force, TF 57, neutralized enemy aircraft on Formosa, the
Pescadores, and Sakishima. 102 The Japanese managed only 50 attacks from 26 March to 31 March
1945, most suicide attacks. Nevertheless, ten American ships were damaged, including the
battleship Nevada, and 74 sailors killed. 103 As the Joint Expeditionary Task Force approached
Okinawa on 31 March 1945, Rear Admiral W.H.P Blandy, the commander of TF 52, reported
that “the preparation was sufficient.” 104
98
99
Ibid., 63.
100
Ibid., 64-65.
101
Ibid.
102
Report of Operations in Ryukyus Campaign, 7-I-3; Appleman, et al., 66.
103
Ibid., 67; Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 45.
104
33
Figure 6. Allied Invasions of Iwo Jima and Okinawa
https://www.usma.edu/history/SiteAssets/SitePages/World%20War%20II%20Pacific/ww
2%20asia%20map%2047.jpg.
Preliminary Landings; 26 March 1945 to 31 March 1945

The first assault troops began landing on 26 March 1945. The 77th Infantry Division,
commanded by Major General Andrew D. Bruce, was responsible for securing positions in the
Kerama Retto and on Keise Shima before to the main landing.
34
Figure 7. Kerama Islands
MAP NO. IV.
The Navy required the Kerama Retto, a group of 22 islands about fifteen miles west of
Okinawa, for a seaplane base and protected boat anchorage. 105 Awaiting the invaders were 975
sailors of the Imperial Japanese Navy Sea Raiding Battalion, as well as another 700 Koreans from
the 103rd Sea Duty Company. 106 However, the real value of Kerama Retto in the defense of the
Ryukyus was the 350 explosive-rigged suicide boats dispersed and hidden throughout the islands.
Preceded by mine clearance and underwater demolition support, four Battalion Landing
Teams of the 77th Infantry landed on Geruma, Hokaji, Aka, Yakabi, and Zamai Shimas around
105
106
Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 38.
35
0930 on 26 March 1945. Geruma, Yakabi, and Hokaji were secured quickly, and two battalions
of 105mm Howitzers were emplaced on Geruma to support subsequent operations in the group.
Resistance proved stiffer on Aka and Zamai, but secure lodgments existed on both islands by
nightfall. Overnight, the enemy mounted counterattacks supported by mortar fire on both islands,
which 77th Division easily defeated.
The next day, 27 March 1945, saw the elimination of organized resistance on Aka and
Zamai, and the subsequent invasion of the largest island, Tokashiki Shima. Progress was quick on
Tokashiki Shima, and the division transitioned to patrolling operations and began reembarking by
28 March. On 29 March 1945, MG Bruce declared the Kerama Retto secure. The islands cost
77th Infantry Division 35 men killed and 67 wounded in exchange for approximately 390
Japanese killed, 99 prisoners captured, and over 250 suicide boats destroyed. 107 Unbeknownst to
either side, securing the Kerama Retto compromised a significant portion of the Japanese A2/AD
plan and cost them any hope of maintaining sea control or preempting the main landing.
The second preliminary objective for 77th Infantry Division was Keise Shima, eleven
miles southwest of the main invasion beach. 77th Infantry Division was directed to secure Keise
Shima and emplace two battalions of M1 155mm guns from the 420th Field Artillery Group to
support the main landings the next day. The Fleet Marine Force Reconnaissance Battalion
reconnoitered Keise Shima on 26 March and encountered no enemy activity. A 77th Infantry
Division BLT landed unopposed on Keise Shima at 0755 on 31 March 1945 and reported the
islands secure at 1015. Next came the 24 guns, 12 of which were in position and ready to fire by
1600. 108 The Japanese 32d Army commander, General Ushijima ordered the American guns
“wiped out,” but shelling throughout the night proved ineffective.
107
Report of Operations in Ryukyus Campaign, 7-II-2.
108
Ibid.
36
With the Ryukyus isolated, air and sea superiority effectively established within the JOA,
and the guns on Keise Shima ready to protect the landing area and interdict reinforcements; the
preliminary conditions were set and the “window of advantage” was open for Tenth Army to land
on L-Day, 1 April 1945.
The Battle of Okinawa; 1 April 1945 to 23 June 1945

At 0406 on Easter Sunday, 1 April 1945, Admiral Turner, the Commander of TF 51, and
the Commander, Amphibious Task Force, gave the order to “land the landing force.” The 1,300
American ships assembled off the coast of Okinawa sprang to life, disgorging their vehicular and
human cargo. At 0530, ten battleships, nine cruisers, twenty-three destroyers, and one hundred
and seventy-seven gunboats initiated “the heaviest concentration of naval gunfire ever to support
a landing of troops.” 109At 0745 carrier aircraft from TF 58 added their bombs and napalm against
known troop positions. A wave of amphibian tanks, followed by five to seven waves of assault
troops crawled slowly toward the Hagushi beaches. 110 H-Hour was 0830, and the first wave was
on-time.
Both corps landed 16,000 assault troops in the first hour on Hagushi Beach astride the
Bishi River; III Amphibious Corps with the 6th and 1st Marine Divisions on the north side, XXIV
Corps with the 7th and 96th Infantry Divisions on the south. 111 There was little organized enemy
resistance to the landing. Far to the south, 2nd Marine Division, still embarked, executed a
successful feint near Minatoga. The landing units assembled quickly, moved inland, and captured
109
110
Ibid., 69-70.
111
Ibid., 72.
37
both Kadena and Yontan airfields by 1130. By nightfall on 1 April, a substantial lodgment had
been established, and 60,000 were ashore. 112
Both corps advanced quickly against light enemy resistance and by 4 April 1945 had
bisected the island and completed their Phase I objectives. Both major airfields were operational
for emergency landings, and Tenth Army occupied a consolidated central position 15 miles long
and 3 to 10 miles wide, and was prepared to turn the attack north and southward. 113
At dawn on 6 April 1945, 400 aircraft from Kyushu attempted to respond to the invasion
but were intercepted by TF 58. Damage to the fleet and the invasion force was relatively light, but
the Japanese lost 300 aircraft. That night, the Imperial Japanese Navy sortied much of its
remaining surface fleet, including the super battleship Yamato, in a suicidal attempt to drive off
the American invasion force. The movement was detected by an American submarine and aircraft
easily located the approaching fleet. The ensuing attacks sank Yamato, a cruiser, and four
destroyers at the cost of cost of ten US aircraft. 114 Japanese forces continued their air and surface
suicide attacks against the American fleet during the remainder of April, costing over 1,100
aircraft and much of their remaining surface force.115 The US Navy lost 4,500 sailors, killed,
missing or wounded. 116 Despite periodic raids throughout the rest of the campaign, the Japanese
defensive plan to drive off the fleet and destroy the invasion force was thwarted, and US air and
sea superiority held.
112
113
Ibid., 83.
114
Ibid., 99.
115
Ibid., 102.
116
Ibid.
38
As the III Amphibious Corps began its Phase II attack to the north on 3 April 1945, the
6th and 1st Marine Divisions found most of their resistance was from the terrain. 117 They reached
Nago on 7 April, cleared the Motobu Peninsula, and isolated and defeated the enemy base in the
Yae-Take on 19 April 1945. Occupying northern Okinawa cost III Amphibious Corps 236 killed
and 1,061wounded in exchange for over 2,500 Japanese killed. 118
Tenth Army’s decisive operation was the XXIV Corps attack to defeat 32d Army and
secure southern Okinawa. Attacking south, divisions abreast, XXIV Corps encountered and
defeated the outposts which protected the First Shuri Defensive Ring by 8 April. From 9 April to
12 April the divisions attempted to penetrate the ring itself, losing 451 soldiers killed in the initial
attacks. 119
On 12 April 32d Army elements, primarily the 62d Division with the attached 22d
Regiment launched a counterattack preceded by a preparatory barrage. The counterattack faltered
and had failed by dawn on 14 April. XXIV Corps spent the next five days mopping up,
integrating 27th Infantry Division on their western flank, and preparing for a coordinated attack
against the Shuri Line on 19 April 1945.
Following the greatest artillery concentration ever employed in the Pacific and
coordinated strikes from 650 Navy and Marine aircraft, XXIV Corps attacked south in zone, three
divisions abreast to seize the town of Shuri and the Yonabaru-Naha Highway on 19 April 1945. 120
The attack broke against the prepared defensive positions and local attacks to reduce them
117
118
Ibid., 148.
119
Ibid., 129.
120
Ibid., 194.
39
continued for several days until 32d Army conducted a coordinated withdrawal on 23 April
1945. 121 The First Shuri Defensive Ring had collapsed.
Sometime between 17 April and 22 April, LTG Buckner made a consequential
series of decisions which prescribed the form of the rest of the operation and remains the most
controversial aspect of Operation ICEBERG. 122 The failure of the 19 April general offensive
dashed any hope of avoiding an attritional slog through southern Okinawa. However, the
availability of the 77th Infantry Division on 21 April offered an alternative option. 77th Infantry
Division had successfully conducted cross-domain maneuver on Leyte, a tactical amphibious
landing in the rear of the Japanese 26th Division defending Ormoc. 123 MG Bruce believed his
division could repeat the maneuver, this time near Minatoga on the southeast coast of Okinawa,
positionally dislocating 32d Army in their directional defensive positions. 124 LTG Buckner
disagreed, judging the operation impracticable and unsustainable, and instead chose to use 77th
Infantry Division to relieve 96th Infantry Division on the battle line.
An opportunity again presented itself on 26 April 1945 when III Amphibious Corps was
released from other obligations for use on Okinawa. Despite strong support for the plan from his
staff, Buckner again declined, and 1st Marine Division also entered the line. Thus, LTG Buckner
recommitted Tenth Army to their attritional frontal attacks against the second Shuri Line. This
decision remains his most controversial. 125
121
122
Ibid., 262.
123
Ibid., 258.
124
Robert Leckie, Okinawa: The Last Battle of World War II (New York, NY: Penguin Books,
1996), 156.
125
Ibid., 158.
40
Tenth Army integrated the fresh III Amphibious Corps and 77th Infantry Division and
prepared to continue its advance south against the Second Shuri Defensive Ring. The attack was
preempted by 32d Army’s final counterattack on 4 May 1945. An extensive artillery barrage and
kamikaze attacks against allied shipping preceded the attack. The plan also included amphibious
envelopments of the Tenth Army line on the east and west. The kamikaze attacks began after
nightfall on 3 May and sank or damaged 17 ships. 126 The amphibious envelopments by the IJN
26th Shipping Engineer Regiment failed miserably costing them almost all their landing craft and
at least 500 men. 127 The attack failed and cost 32d Army 5,000 troops. 128 General Ushijima
realized this fact and announced to his command that henceforth “the battle plan in the Shuri area
sector will be an attrition of enemy strength until he has lost his endurance.” 129
After the failed counterattack, General Buckner notified his command that the next phase
in the campaign, “a continuation of the type of attack we have been employing to date,” would
commence on 11 May 1945 with Shuri as its objective. 130 The attack began on 11 May and true to
General Buckner’s pronouncement was more of the same. Progress was slow, ridgeline-by-
ridgeline, and the advance was interrupted by foul weather from 22 May to 29 May which
hampered ground movement and close air support. The Japanese seized upon the weather to
renew their air attacks against the air and naval forces protecting Okinawa. Of note, 69 Japanese
airborne soldiers attempted an air assault against Yontan Airfield using low-flying bombers on 24
May 1945. Though only ten soldiers penetrated the bases air defenses, those they damaged or
126
127
Ibid., 289.
128
Ibid., 302.
129
Ibid.
130
Ibid., 312.
41
destroyed 33 aircraft on the ground, ignited 140,000 gallons of gasoline, and shut down the
airstrip until the following day. 131 Kamikaze attacks against naval vessels also intensified,
damaging 21 ships. 132
The principal commanders of the 32d Army met at Shuri on 22 May 1945 to consider the
course of future operations. 133 After discussion, General Ushijima resolved to withdraw and make
his final stand in the south. The movement began immediately and occurred largely unbeknownst
to Tenth Army; only a three-battalion holding force remained at Shuri.
The defeat of the holding force and occupation of Shuri began on 29 May, and by 31 May
1945, the hub of the Shuri defensive perimeter was finally in Tenth Army hands. As May ended,
Tenth Army’s losses totaled 26,044 killed, wounded, or missing while 32d Army units reported
62,548 killed. 134 Tellingly, only 218 Japanese soldiers were taken alive. 135
Having taken Shuri largely unopposed, the first order of business was to prevent 32d
Army from escaping. “It’s all over now but cleaning up pockets of resistance,” declared General
Buckner. 136 However, as usual on Okinawa, the weather intervened, and 32d Army escaped to
form a new defensive ring centered on its headquarters at Hill 89 near Mabuni.
When the rains ceased on 5 June 1945, XXIV Corps faced a massive defended
escarpment anchored by defended positions on the east and west coast and in the center by the
Yaeju-Dake and Yuza-Dake peaks. Beyond the escarpment lay a tableland, 11,000 Japanese
infantrymen, and the sea. 137 XXIV Corps attacked this line against stiff resistance on 6 June 1945.
131
Appleman, et al., 361-362; Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 200.
132
Ibid., 362.
133
Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 207-208.
134
135
Ibid., 384.
136
Ibid., 422.
137
Ibid., 436.
42
As the XXIV Corps and III Amphibious Corps attacks proceeded, they perceived a weakening of
resistance.
The final phase began in the XXIV Corps sector on 13 June 1945. Infantrymen of the 7th
and 96th Infantry Divisions in concert with flame tanks of the 713th Armored Flame Thrower
Battalion cooperated to great effect. On 18 June 1945, the remnants of 32d Army began to
collapse. General Ushijima ordered his remaining soldiers to infiltrate north and begin a
campaign of guerrilla warfare. Hundreds took him up on this offer; others surrendered en masse.
LTG Buckner was killed by Japanese artillery on 18 June while observing the fighting and was
replaced first by Marine Major General Roy Geiger, then by General Joseph Stilwell.
As Tenth Army converged on Hill 89, they reduced the remaining enemy positions. On
21 June 1945, the U.S. 32d Infantry Regiment began its assault on Hill 89 itself. That night,
General Ushijima, 32d Army Commander, and his Chief of Staff committed ritual suicide. 138 The
next day, 22 June 1945, the last pocket of organized resistance fell.
On 23 June 1945, Tenth Army began mopping-up the disorganized stragglers persisting
in their rear area. The corps turned and cleared back northward, killing 8,975 Japanese soldiers
before halting on 30 June 1945. 139 The campaign ended on 2 July 1945. Operation ICEBERG
cost the United States 12,520 killed, and 36,631 wounded. 140 Slowing US progress toward the
Home Islands for 83 days cost Japan approximately 110,000 lives. 141
138
Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 258.
139
140
Ibid., 473.
141
Ibid., 473-474.
43
Figure 8. Operations in Southern Okinawa
https://www.westpoint.edu/history/SiteAssets/SitePages/World%20War%20II%20Pacific/
ww2%20asia%20map%2049.jpg.
44
Analysis and Recommendations
In Multi-Domain Battle: A Perspective on the Salient Features of an Emerging
Operational Doctrine, Major Amos Fox describes the characteristics of the peer adversaries
likely to be faced by the United States in the near future as having “layers to their force, much
like the layers of an onion obfuscate each subsequent layer.” 142 Fox proposes that to defeat this
type of enemy, US forces must first “debride” the outer layers of long-range and cross-domain
forces to access and defeat the main fighting force inside. 143 The Multi-Domain Battle Concept
introduces convergence as the mechanism to affect this “debridement,” describing it as follows:
Convergence is the integration of capabilities across domains, environments, and

functions in time and physical space to achieve a purpose. Converging capabilities is a
new idea introduced in Multi-Domain Battle as an evolution of combined arms.
Convergence is the act of applying a combination of capabilities (lethal and nonlethal,
whether within a domain or cross-domain) in time and space for a single
purpose…Although the ideas within convergence are an evolution of combined arms
principles and practices, the Joint Force requires significantly new doctrine,
organizations, and capabilities to integrate the full range of capabilities across time and
space to create windows of advantage that enable maneuver in contested spaces. 144
The layered anti-access/area denial strategy employed by the Japanese defending the
Ryukyus mirrors Fox’s onion analogy. Like the enemy envisioned in the Multi-Domain Battle
Concept, the Japanese forces defending Okinawa remained more than capable of contesting US
access in the three accessible domains; maritime, air, and land. To create the windows of
advantage needed for Tenth Army to land, maneuver, and defeat the 32d Army and secure the
necessary air and sea bases to press the attack against the Japanese home islands, the planners of
Operation ICEBERG deliberately converged strategic, operational, and tactical capabilities, often
142
Amos C. Fox, "Multi-Domain Battle: A Perspective on the Salient Features of an Emerging
Operational Doctrine," Small Wars Journal, May 21, 2017, 2, accessed 06 October 2017,
http://smallwarsjournal.com/jrnl/art/multi-domain-battle-a-perspective-on-the-salient-features-of-an-
emerging-operational-doctri.
143
Ibid.
144
45
across domains. The resulting concentric “debridement” of Okinawa’s air and sea defenses
provides a theoretical model for visualizing how a near-future joint force can create windows of
advantage to enable maneuver in the archipelagic environment typical in the Indo-Asia Pacific.
Convergence in Operation ICEBERG

The plan for Operation ICEBERG employed convergence of strategic, operational, and
tactical capabilities, often across domains, to defeat Japan’s A2/AD strategy, and enable ground
maneuver in a contested space. Admiral Chester Nimitz, the CINCPOA, recognized that as the
allied noose tightened around the home islands, Japan’s remaining air and sea forces would
become further concentrated. 145 This allowed them to offer progressively stronger resistance as
American forces approached the southernmost Japanese island of Kyushu. Nimitz appreciated
this threat and his Concept of the Operation, described in the Joint Staff Study for ICEBERG,
makes establishing “undisputed control of the sea and air in the area of operations” essential to its
success. 146
145
146
Joint Staff Study: ICEBERG, 2-3.
46
Figure 9. Converging Capabilities in Operation ICEBERG
Source: Created by the author from Multi-Domain Battle: Evolution of Combined Arms for the
21st Century (Fort Eustis, VA: US Army Training and Doctrine Command, 2017), 9.
Air and sea control were accomplished by neutralizing Japanese air and naval forces and
installations, then isolating the JOA. Before the amphibious task force entered the Ryukyus, the
raiding Fast Carrier Tasks Force and long-range strategic bombers operating from China, the
Marianas, and Luzon destroyed major Japanese air bases in the southern home islands, Formosa,
Amoy, and the Pescadores. 147 Submarine and surface attacks against Japanese shipping severed
Okinawa’s sea lines of communication. The objective of this preparatory phase was to isolate
Okinawa. 148
As the amphibious task force prepared to enter the Ryukyus, preceded by minesweepers,
strategic bombers and carrier aircraft continued their attacks against Japanese facilities
147
Joint Staff Study: ICEBERG, 3.
148
47
throughout the theater, striking targets in Hong Kong, Formosa, Kyushu, the Pescadores, and
Sakishima. 149 Preparatory air and surface strikes against air bases and naval facilities within the
Ryukyus commenced on 17 March 1945. The coordinated converging effect of these strategic and
operational capabilities established “a sphere of air and sea superiority in the Okinawa Gunto;”
effectively a window of advantage. 150
Of note during this period were two subsidiary landings conducted by the 77th Infantry
Division in the Kerama Retto beginning on 26 March 1945, and on Keise Shima on 31 March
1945. The amphibious invasion of the Kerama Retto is significant because it demonstrates the
value of land forces conducting “semi-independent, cross-domain maneuver” to enable
capabilities in adjacent contested domains. 151 Initially intended to secure a protected fleet
anchorage and seaplane base for the naval forces supporting the main landing, physically
occupying the Kerama Retto contributed enormously to establishing sea superiority in an
unanticipated way. Dispersed and concealed throughout the islands were more than 350
explosive-laden suicide boats belonging to the IJN Sea Raiding Squadrons. 152 These boats were a
critical component of the Japanese plan to contest the allied landing by destroying the US troop
transports as they approached the landing beaches. The unexpected introduction of land forces to
systematically clear the Kerama Retto led to the neutralization of a critical enemy A2/AD
capability which had remained largely unaffected by naval and air bombardment alone. The 77th
Infantry Division had completely frustrated the Japanese defensive plan.153 This ability to
149
Report of Operations in Ryukyus Campaign, 7-I-3.
150
Ibid., 7-I-1.
151
152
153
Ibid., 60.
48
decisively defeat enemy forces and clear terrain proved essential to the success of Operation
ICEBERG and remains the exclusive domain of land power.
The second subsidiary landing undertaken by 77th Infantry Division prior to L-Day was
the unopposed landing of a Battalion Landing Team (BLT) and twenty-four M1 155mm
howitzers from the 420th Field Artillery Group on Keise Shima on 31 March 1945 to provide
persistent counterbattery, interdiction, and harassing fires against the Hagushi beaches and most
of southern Okinawa. 154 The Japanese, belatedly realizing the value of the position, attempted to
dislodge the guns throughout the night but were unsuccessful. Though the Japanese also failed to
drive off the fire support ships accompanying the main landing force, the firing battalions on
Keise Shima still provided invaluable counterbattery and interdiction fires to isolate the
beachhead. The 77th Infantry Division Battalion Landing Team demonstrates the necessity of
incorporating a land combat force to enable and protect the employment of long-range fires
platforms.
The final, tactical component of the capabilities converging to create the window of
advantage for Tenth Army to maneuver was the initial landing forces themselves. A factor in
selecting the Hagushi beaches as the primary landing site was their proximity to the major
Japanese airfields at Kadena and Yontan. US forces captured both airfields within four hours of
the arrival of the initial wave, and both were operational for emergency landings by the end of L-
Day. 155 Land-based fighter aircraft were operating at both locations by 9 April 1945, further
solidifying allied air superiority in the Ryukyus. 156
The massive strategic, operational, and tactical convergence of allied capabilities proved
overwhelmingly successful in establishing air and sea superiority in the Ryukyus. The main
154
155
Ibid., 81.
156
Ibid., 83.
49
landings on 1 April 1945 were relatively unmolested by Japanese air and sea forces. No
substantial Japanese response materialized until 6 April 1945 when a massive 400-plane raid
staged from Kyushu managed to damage Kadena and sink several ships, including two
destroyers. 157 These raids continued periodically throughout April and May, proving costly but
never seriously jeopardizing Tenth Army’s operations. This historical example of convergence
successfully producing a window of advantage to enable maneuver is the primary contribution of
Operation ICEBERG to future Multi-Domain Battle in the Indo-Asia Pacific; demonstrating the
practicability of the concepts of convergence and windows of advantage and providing a
theoretical model for their visualization.
Recommendations
Tenth Army’s activities during Operation ICEBERG inform possible adaptations to the
training, preparation, and employment of Army forces in future Multi-Domain Battle in the Indo-
Asia Pacific.
Tenth Army was a joint organization composed of an Army Corps, a Marine Amphibious
Corps, an Army Garrison Force, a Tactical Air Force, and an assigned Naval Force. LTG
Buckner’s efforts to enhance interservice coordination at the headquarters-level during planning
and execution are well documented. 158 However, several organizational adaptations occurred at
the subordinate unit-level which challenge the contemporary “federated” vision of joint
operations synchronized primarily at the JTF-level. Some examples, such as the attachment of
modified M-4 Sherman flame tanks from the Army 713th Armored Flamethrower Battalion to the
Marine Divisions to reduce defensive positions using “blowtorch and corkscrew” tactics would
157
158
Report of Operations in Ryukyus Campaign, 3-0-3; Appleman, et al., 27.
50
not be unfamiliar in contemporary operations. 159 Others like the assignment of Navy fire support
ships in direct support of Army and Marine regiments and divisions would be unlikely in a
modern JTF. 160 The Tenth Army vision of joint operations, from the Army headquarters to the
tank-infantry teams, should become a central organizing principle for land combat forces
assigned to the Indo-Asia Pacific. They should train jointly to build familiarity and be employed
jointly during competition, and in the event of armed conflict.
The forces assigned to Tenth Army for Operation ICEBERG presented substantial
challenges with regards to force posture. Due to a shortage of available troops, those assigned
were scattered throughout the Pacific, in most cases at the division and below-level. The III
Marine Amphibious Corps had divisions on the Russell Islands, Saipan, and Guadalcanal. The
XXIV Corps with its subordinate divisions, the 7th, 77th, and 96th Infantry Divisions, was
engaged in active combat in Leyte until February 1945. 161 The 27th Infantry Division, the floating
reserve, was at Espiritu Santo recovering from the Battle of Saipan the previous summer. Tenth
Army Headquarters and staff, along with many of its supporting units and naval augmentation
loaded out at or passed through Oahu. 162
This disposition approximates the calibrated forward presence likely to be encountered
by Army land combat forces scattered throughout the Indo-Asia Pacific executing military
competition activities. In the event of an escalation to armed conflict, the Multi-Domain Battle
Concept states that these forward presence forces “must have the expeditionary capacity,
159
Appleman, et al., 256; Nichols and Shaw, Jr., Okinawa: Victory in the Pacific, 272.
160
Ibid., 253.
161
162
Ibid., 5-0-8.
51
including strategic lift, to maneuver directly from home station or other theaters of operation into
battle.” 163
Coordinating this strategic and operational maneuver for the dispersed forces assigned to
Tenth Army consumed much of the staff’s planning effort in the months preceding the invasion.
Transport Quartermasters at the various headquarters developed and published a system of
procedures governing the process. Responsibility for loading-out and embarkation then devolved
to the assigned unit headquarters and local Transport Quartermaster Teams attached for this
purpose. 164 Though not specifically recorded, much of the success of this process was probably
still dependent on prior individual experience in similar operations. Regardless of the means
employed for strategic or operational maneuver, if dispersed forward presence forces are
expected to rapidly aggregate in contested spaces, they should be familiarized with established
procedures and provided the necessary personnel or training to accomplish this before assuming
their forward presence. The historical example of Operation ICEBERG provides a conceptual
model for anticipating and developing these requirements.
Questions for Further Study

To further explore the preparation and employment of Army land combat forces in future
Multi-Domain Battle in the Indo-Asia Pacific, the following questions are proposed for further
study:
1. What is an appropriate standing headquarters to coordinate regional forward
presence forces during competition and employ them during anticipated near-future armed
conflict in the Indo-Asia Pacific?
163
164
52
2. Can this headquarters be constituted as a standing joint headquarters?
3. How do forward-positioned forces and reinforcing rapidly deployable formations
effectively execute expeditionary maneuver within the denied or contested environments posited
by Multi-Domain Battle given the nature of the Indo-Asia Pacific region?
Conclusion
In Preparing for the Fight Tonight, General David Perkins observes that “the most
egregious doctrinal void had been the lack of principles for multi-domain capabilities in large-
scale combat operations.” 165 He adds that “The Army and the other services must be able to
converge capabilities across multiple domains in an integrated fashion to gain and then exploit the
initiative.” Sharing the geography of the Pacific and an enemy capable of denying or contesting
US dominance in all the domains, Operation ICEBERG provides a successful contemporary
example of strategic, operational, and tactical convergence of joint and cross-domain capabilities
to inform the development of Multi-Domain Battle in the Indo-Asian Pacific. If Operation
ICEBERG is the culmination of all our experiences fighting our last major war against a peer
competitor in the Indo-Asia Pacific, we would be foolish to prepare for the next war without
heeding the lessons of the “Last Battle.”
165
David G. Perkins, "Preparing for the Fight Tonight: Multi-Domain Battle and Field Manual
3.0," Military Review, September 2017, 11, accessed 08 October 2017, www.armyupress.army.mil
/Portals/7/military-review/Archives/English/ PERKINS_II_Preparing_for_the_Fight_Tonight.pdf
53
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From “Last Battle” to the Next War: Using Operation

ICEBERG to Inform Multi-Domain Battle in the

MAJ Jonathan C. Leiter

School of Advanced Military Studies

Approved for Public Release; Distribution is Unlimited

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__________________________________, Monograph Director

__________________________________, Seminar Leader

___________________________________, Director, School of Advanced Military Studies

Accepted this 24th day of May 2018 by:

___________________________________, Director, Graduate Degree Programs

Acronyms ...................................................................................................................................... vii

Illustrations ................................................................................................................................... viii

The Problem ................................................................................................................................ 3

The Research Question ............................................................................................................... 6

Secondary Questions ................................................................................................................... 6

Operation ICEBERG: Proto-Multi-Domain Battle in the Indo-Asia Pacific .............................. 8

Scope and Limitations and Delimitations ................................................................................... 9

Multi-Domain Battle ...................................................................................................................... 11

Competition vs. Armed Conflict ............................................................................................... 12

The Expanded Battlespace ........................................................................................................ 14

Calibrate Force Posture: ............................................................................................................ 15

Employ Resilient Formations: .................................................................................................. 15

Converge Capabilities: .............................................................................................................. 16

Case Study ...................................................................................................................................... 17

Operation ICEBERG ................................................................................................................ 17

The Joint Operations Area (JOA) ............................................................................................. 17

The Belligerents ........................................................................................................................ 21

Immediate Military Objectives of Operation ICEBERG .......................................................... 26

Preliminary Operations; 10 October 1944 to 31 March 1945 ................................................... 30

Preliminary Landings; 26 March 1945 to 31 March 1945 ........................................................ 34

The Battle of Okinawa; 1 April 1945 to 23 June 1945 ............................................................. 37

Analysis and Recommendations..................................................................................................... 45

Convergence in Operation ICEBERG ...................................................................................... 46

Questions for Further Study ...................................................................................................... 52

Print Sources ............................................................................................................................. 54

Online Sources .......................................................................................................................... 55

and loving me anyway…

AAF Army Air Forces

AUSA Association of the United States Army

BCT Brigade Combat Team

BLT Battalion Landing Team

CATF Commander of the Amphibious Task Force

CinCPOA Commander in Chief, Pacific Ocean Areas

CLF Commander of the Landing Force

IJA Imperial Japanese Army

IJN Imperial Japanese Navy

JCS Joint Chiefs of Staff

JOA Joint Operations Area

JTF Joint Task Force

LTG Lieutenant General

MDB Multi-Domain Battle