Nuclear Weapons and International Conflict - Theories and Empirical Evidence
Nuclear Weapons and International Conflict - Theories and Empirical Evidence
Nuclear Weapons and International Conflict - Theories and Empirical Evidence
Evidence
Since 1945, a vast, sophisticated, and contradictory literature has developed on the
implications of nuclear weaponry for patterns of international conflict and war. This
theoretical and empirical work has principally focused on the conflict effects of these
weapons for the interaction of nuclear-armed states, although a growing number of
studies have explored the impact of a state’s possession of nuclear weapons on the
behavior of nonnuclear opponents. Given the destructive capacity of these weapons and
their questionable value for battlefield use, most of this work has concentrated on the
requirements for successful deterrence. In categorizing the studies, some scholars note
that “classical deterrence theory” derives from the Realist paradigm of international
politics and subdivide this theory into two complementary strands: structural (or
neorealist) deterrence theory and decision-theoretic deterrence theory. In contrast, other
analysts choose to classify work on nuclear deterrence into three schools of thought:
nuclear irrelevance; risk manipulation, escalation, and limited war; and the nuclear
revolution. The essence of these divisions involves a debate about what the possession of
nuclear weapons does for a state that controls them. Does the possession of these
weapons affect the behavior of nuclear and non-nuclear opponents in disputes over
contested values? Do the weapons impart political influence and hold military utility, or
are they useless as tools for deterrence, compellence, or war?
Keywords: nuclear weapons, deterrence, crisis escalation, nuclear war, international conflict, empirical
international relations theory
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Introduction
The balance of conventional military capabilities is intrinsic to understanding patterns of
war among nations (Geller, 2000A). However, cumulative knowledge relating to the
effects of nuclear weapons possession on conflict interaction is largely absent. This
article seeks to provide a framework for analyzing the results of quantitative empirical
research on this question and to identify any extant strong and consistent patterns in the
interactions of states that can be associated with the possession of nuclear weapons.
Since 1945, a vast, sophisticated, and contradictory literature has developed on the
implications of nuclear weaponry for patterns of international conflict and war.1 This
theoretical and empirical work has principally focused on the conflict effects of these
weapons for the interaction of nuclear-armed states, although a growing number of
studies have explored the impact of a state’s possession of nuclear weapons on the
behavior of nonnuclear opponents. Given the destructive capacity of these weapons and
their questionable value for battlefield use, most of this work has concentrated on the
requirements for successful deterrence. In categorizing the studies, Zagare and Kilgour
(2000), for example, note that “classical deterrence theory” derives from the Realist
paradigm of international politics, and they subdivide this theory into two complementary
strands: structural (or neorealist) deterrence theory and decision-theoretic deterrence
theory. In contrast, Jervis (1979, 1984, 1988), among others, chooses to classify work on
nuclear deterrence into three schools of thought: nuclear irrelevance; risk manipulation,
escalation, and limited war; and the nuclear revolution. The essence of these divisions
involves a debate about what the possession of nuclear weapons does for a state that
controls them. Does the possession of these weapons affect the behavior of nuclear and
non-nuclear opponents in disputes over contested values? Do the weapons impart
political influence and hold military utility or are they useless as tools for deterrence,
compellence, or war?
Nuclear strategy has principally concerned itself with the efficacy of nuclear weapons as
a deterrent. One school of thought—nuclear revolution theory—characterized by the
works of Brodie (1946, 1959, 1978), Waltz (1981, 1990, 1993, 2003), and Jervis (1984,
1988, 1989A), holds that the incredibly rapid and destructive effects of nuclear weapons
creates a strong disincentive for nuclear-armed states to engage each other in disputes
that might escalate to the level of war. The “nuclear revolution” means that nuclear
weapons can deter aggression at all levels of violence and makes confrontations and
crises between nuclear-armed states rare events. The maintenance of a nuclear second-
strike capability is all that is required for a successful military deterrent force.
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Over the past thirty-five years, large-scale quantitative empirical studies have attempted
to generate evidence relating to these theories. Discussion of some of these works
follows.
Theory
The term “nuclear revolution” was coined by Robert Jervis (1989A, ch. 1), although the
initial recognition of the alterations in patterns of international politics likely to be
wrought by nuclear weapons should be credited to Bernard Brodie (1946). As Jervis has
noted:
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Moreover, for Jervis (1989B), that this destruction was essentially unavoidable under any
plausible strategy constituted the essence of the nuclear revolution. Jervis (1989A, pp.
23–25) went on to enumerate changes in international politics directly attributable to the
presence of nuclear weaponry, including the absence of war among the great powers, the
declining frequency of great power crises, and the tenuous link between the conventional
or nuclear balance among great powers and the political outcomes of their disputes.3
Kenneth Waltz (1981, 1990, 1993, 2003, 2008) has been exceptionally prominent in
developing and forwarding the thesis that nuclear weapons are a force for peace and that
nuclear proliferation will lead to declining frequencies of war. Waltz argues that nuclear
weapons are simply more effective in dissuading states from engaging in war than are
conventional weapons:
In a conventional world, states going to war can at once believe that they may win
and that, should they lose, the price of defeat will be bearable (Waltz, 1990, p.
743). A little reasoning leads to the conclusions that to fight nuclear wars is all but
impossible and that to launch an offensive that might prompt nuclear retaliation is
obvious folly. To reach these conclusions, complicated calculations are not
required, only a little common sense (Waltz in Sagan & Waltz, 1995, p. 113). The
likelihood of war decreases as deterrent and defensive capabilities increase.
Nuclear weapons make wars hard to start. These statements hold for small as for
big nuclear powers. Because they do, the gradual spread of nuclear weapons is
more to be welcomed than feared.
Given this logic, evidence consistent with an absence of war or the use of force short of
war between nuclear-armed states and few (or a declining frequency of) crises between
nuclear powers would be supportive of the nuclear revolution thesis.
Empirical Evidence
A number of quantitative empirical studies have produced evidence relevant to the
nuclear revolution thesis. In an early study of the effects of nuclear weapons possession,
Bueno de Mesquita and Riker (1982) present both a formal mathematical model and an
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Asal and Beardsley (2007) examine the relationship between the severity of violence in
international crises and the number of states involved in the crises that possess nuclear
weapons. Using data from the International Crisis Behavior (ICB) Project for the years
1918 through 2000, their results indicate that crises in which nuclear actors are involved
are more likely to end without violence and that, as the number of nuclear-armed states
engaged in crises increases, the probability of war decreases. This evidence is
interpreted as supportive of the nuclear revolution thesis: the presence of nuclear
weapon states in international crises has a violence-dampening effect due to the potential
consequences of escalation and the use of nuclear force.
In a second study, Beardsley and Asal (2009A) hypothesize that nuclear weapons act as
shields against aggressive behavior directed toward their possessors. Specifically, it is
postulated that nuclear states will be constrained in engaging in aggressive actions
toward other nuclear-armed powers. Data is drawn from the ICB Project for the years
1945 through 2000, using directed dyads as the unit of analysis. The results indicate that
nuclear opponents of other nuclear-armed powers are limited in their use of violent force.
However, Beardsley and Asal (2009A, p. 251) also note that the “restraining effect of
nuclear weapons on violent aggression does not appear to affect the propensity for actors
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Additional results consistent with the nuclear revolution thesis are reported in a study by
Sobek, Foster, and Robinson (2012). Using directed-dyad year with MID data for the
period between 1945 and 2001, the study examines the effects of efforts to develop
nuclear weapons on the targeting of the proliferator in militarized disputes. Sobek et al.
(2012, p. 160) conclude that “. . .if a state . . . gains nuclear weapons, then the odds of
being targeted in a militarized dispute falls.” States developing nuclear weapons are
high-frequency targets in MIDs, but “. . .[t]argeting drops precipitously when [joint]
acquisition is achieved” (Sobek et al., 2012, p. 160).
However, Bell and Miller (2015) present evidence that is counter to the preceding
studies. Using data collected by Rauchhaus (2009), they contend that nuclear dyads are
neither more nor less likely to fight wars or engage in sub-war conflicts than are
nonnuclear dyads. They argue that the evidence indicating a strong negative probability
of war in symmetric nuclear dyads is due to the statistical model used by Rauchhaus,
whereas the positive association for nuclear dyads and crisis frequency reported by
Beardsley and Asal (2009A) is due to selection effects (i.e., nuclear weapons possession is
more a consequence rather than a cause of conflict).
Evaluation
The nuclear revolution thesis maintains that there should be a general absence of war or
the use of force short of war among nuclear-armed states. In addition, there is the
expectation of few (or a diminishing number of) crises in nuclear dyads, as the fear of
escalation will exert a powerful constraint on aggressive behavior.
Bueno de Mesquita and Riker (1982) present compelling evidence that nuclear
asymmetry or the absence of nuclear weapons on both sides of a conflict are more likely
to be associated with war. In their data, between 1945 and 1976, there were 17 cases of
war between nonnuclear states, two cases of war in asymmetric nuclear dyads, and zero
cases of war in either nuclear dyads or nuclear/nonnuclear dyads where the nonnuclear
party had a nuclear-armed ally. Rauchhaus’ (2009) study also presents evidence that
symmetric nuclear dyads are unlikely to engage in war. The article by Asal and Beardsley
(2007) reports results consistent with those of Bueno de Mesquita and Riker (1982).
Specifically, crises ending in war are not uncommon for confrontations engaging
nonnuclear states and for confrontations in which only one state possesses nuclear
weapons. However, as the number of nuclear participants increases beyond one, the
probability of full-scale war diminishes. Only the results of Bell and Miller (2015) stand in
contrast with the findings on symmetric nuclear dyads and the probability of war.
Similarly, Beardsley and Asal (2009A) show findings consistent with the nuclear
revolution thesis: symmetric nuclear dyads engage in few crises where violence is the
“preeminent” form of interaction. This conclusion is also supported by the findings
reported by Sobek et al. (2012). However, Asal and Beardsley (2007) and Beardsley and
Asal (2009A) also note that there appears to be no constraining effect produced by
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Since the advent of nuclear weapons in 1945, there has been one war between nuclear-
armed powers: the Kargil War of 1999 involving India and Pakistan (Geller, 2005, p. 101).
This conflict remained at the conventional level and surpassed the threshold of 1,000
battle deaths set by the Correlates of War Project for classification as a war (Singer &
Small, 1972; Small & Singer, 1982). However, Paul (2005, p. 13) argues that, despite the
conventional military asymmetry between India and Pakistan (in India’s favor) that
existed at the time of the Kargil War, the development of Pakistani nuclear weapons
actually permitted Pakistan to launch a conventional invasion of the disputed territory of
Kashmir. As Paul explains, only in a long war could India mobilize its material superiority,
but as a result of the development of Pakistani nuclear weapons, a long war becomes
“inconceivable” without incurring the risk of nuclear escalation. Hence, Pakistan’s
leaders were emboldened to initiate a conventional war behind the shield of their nuclear
deterrent despite their conventional military inferiority. This sole case of conventional
war between nuclear-armed states—and its facilitation by the risk of unacceptable
escalation provided by nuclear weapons—stands in stark contradiction to the predictions
of nuclear revolution theory.5
These collective results provide only partial support for the nuclear revolution thesis. As
the theory suggests, war between nuclear-armed states should be nonexistent or a very
rare event. This prediction, to date (with one notable exception), has been upheld.
However, Beardsley and Asal (2009A) report that symmetric nuclear dyads engage in an
unexpectedly large number of crises—in contradiction to the predictions of nuclear
revolution theory. This is an empirical question that will receive additional examination in
the following section.
Theory
A second school of thought—risk manipulation, escalation, and limited war—finds its
archetypal expression in the seminal work of Henry Kissinger (1957). According to this
thesis (and counter to that of nuclear revolution theory), the possession of a nuclear
second-strike capability may deter a nuclear attack by an opponent on one’s home
territory, but not much else. Kissinger argued that the United States (and its NATO allies)
required the ability to conduct successful combat operations at levels of violence below
that of general nuclear war if the protection of Europe against Soviet aggression was a
political goal. Some years later, Snyder (1965) discussed this as what was later termed
the “stability-instability paradox.” The essence of the paradox was that stability at the
level of general nuclear war permitted the exploitation of military asymmetries at lower
levels of violence—including strategic (counterforce) and tactical nuclear wars as well as
conventional forms of combat. The thesis that strategic nuclear weapons possessed little
political or military utility other than deterring a nuclear attack on one’s home territory
led to a number of works devoted to the analysis of tactics for coercive bargaining and
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As Snyder and Diesing (1977, p. 450) maintain, the primary effect of the possession of
nuclear weapons on the behavior of nuclear adversaries is the creation of new constraints
on the ultimate range of their coercive tactics—a result of the extraordinary increase in
the interval between the value of the interests at stake in a conflict and the potential
costs of war. They note that before the advent of nuclear weapons, this interval was
comparatively small and states could more readily accept the risk of war in a coercive
bargaining crisis or engage in war in order to avoid the loss of a contested value. In
contradistinction, given even small numbers of nuclear weapons in the stockpiles of
states, it is far more difficult to conceive of an issue worth incurring the high risk of
nuclear war, much less the cost of actually fighting one.7
According to this thesis, a direct result of the constraints created by the presence of
nuclear weapons has been the attempt by nuclear powers to control, in a more finely
calibrated manner, the threat and application of force in disputes with other nuclear-
armed states. These developments find theoretical and empirical expression in the
concept of escalation, which is defined as the sequential expansion of the scope or
intensity of conflict (Osgood & Tucker, 1967, p. 127, 188).8 In most standard
formulations, escalation is conceived as a generally “controllable and reversible
process,”9 which a rational decision maker can employ in conflict situations as an
instrument of state policy (Osgood & Tucker, 1967, p. 188). Decision makers estimate the
relative bargaining power of the rivals and engage in increasingly coercive tactics that
are designed to undermine the opponent’s resolve. Controlled escalation occurs when
each side is capable of inflicting major or unacceptable damage on the other but avoids
this while attempting to influence the opponent with measured increases in the conflict
level that incorporate the threat of possible continued expansion.
The measured application of force and the ability to control escalation in nuclear disputes
are seen—by these strategic theorists—as indispensable for securing political values
while minimizing risk and cost (Osgood & Tucker, 1967, p. 137; Russett, 1988, p. 284). A
preeminent theorist in this school, Herman Kahn (1965, p. 3), described escalation as “an
increase in the level of conflict . . . [often assuming the form of] a competition in risk-
taking or . . . resolve.” As this theory developed, conflict analysts elaborated the risks
involved in the process and incorporated the manipulation of these risks as a possible
tactic in one’s strategy.10
Clearly, nuclear weapons have not altered the values at stake in interstate disputes (and
the desire to avoid political loss), but rather have increased the rapid and immediate
costs of war. As a result, in a severe conflict between nuclear powers, the decision
maker’s dilemma is to construct a strategy to secure political interests through coercive
actions that raise the possibility of war without pushing the risk to an intolerable level.
Some analysts argue that the solution to this problem has entailed an increase in the
“threshold of provocation,” providing greater area of coercive maneuver in the threat,
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It is frequently stated that the principal exemplar of this new form of competition is the
local crisis. Obviously, crises have an extensive history in international politics, but the
argument is made that the nuclear age has produced an expansion of steps on the
escalation ladder and has intensified the maneuvering of nuclear rivals for dominant
position in conflicts below the level of all-out war. For example, Snyder and Diesing note
that:
the expanded range of crisis tactics in the nuclear era can be linked to a new
conception of crises as surrogates for war, rather than merely dangerous incidents
that might lead to war. . . [S]ince war is no longer a plausible option between
nuclear powers, they have turned to threats of force and the demonstrative use of
force short of war as a means of getting their way. The winner of the encounter is
the one who can appear the most resolved to take risks and stand up to risks.
Given this logic, conflicts between nuclear powers should reveal different escalatory
patterns than conflicts between states where only one side possesses nuclear arms, or
conflicts where neither side possesses nuclear arms. Specifically, disputes between
nuclear powers should evidence a greater tendency to escalate—short of war—than
nonnuclear disputes or disputes, in which only one side possesses a nuclear capability.
Empirical Evidence
Kugler (1984) presents an empirical test of classical nuclear deterrence theory: the study
examines whether nuclear weapons are salient in preventing the initiation or escalation
of war to extreme levels. The analysis focuses on crisis interactions involving the United
States, the Soviet Union, and China (PRC) with the case set drawn from Butterworth
(1976) and CACI (Mahoney & Clayberg, 1978, 1979). The cases used in the analysis
constitute 14 extreme crises where nuclear nations were involved and where nuclear
weapons “played a central role” (Kugler, 1984, p. 477). The results indicate that crises of
extreme intensity diminish as the threat of nuclear devastation becomes mutual. In other
words, as the capacity of actors to destroy each other with nuclear weapons increases,
there is a tendency to decrease the intensity of conflict, and to settle those crises that
reach extreme proportions by compromise. This suggests that deterrence of war through
the symmetric possession of nuclear weapons is operative in the conflict dynamics of
great-power crises.
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Huth, Gelpi, and Bennett (1993) analyze 97 cases of great power deterrence encounters
from 1816 to 1984 as a means of testing the explanatory power of two competing
theoretical approaches to dispute escalation. Dispute escalation is defined as the failure
of the deterrent policies of the defender. Deterrence failure occurs when the
confrontation ends in either the large-scale use of force or defender capitulation to the
challenger’s demands. For the post-1945 period, the findings indicate that, for nuclear
dyads, the possession of a nuclear second-strike capability by the defender substantially
reduces the likelihood of the confrontation ending either in war or in capitulation by the
defender. However, the possession of nuclear weapons in great power dyads does not
deter the challenger from initiating militarized disputes.
Asal and Beardsley (2007) examine the relationship between the severity of violence in
crises and the number of states involved in the confrontations that possess nuclear
weapons. Using data from the International Crisis Behavior (ICB) Project, the study
includes 434 international crises extending from 1918 through 2001. The results indicate
that symmetric nuclear dyads engage in an unexpectedly large number of crises—and
that “crises involving nuclear actors are more likely to end without violence. . . [A]s the
number of nuclear actors increases, the likelihood of war continues to fall” (Asal &
Beardsley, 2007, p. 140). The authors also note that their results indicate that there may
be competing effects within nuclear dyads: specifically, that both sides will avoid war but
engage in sub-war levels of escalatory behavior (Asal & Beardsley 2007, p. 150, fn. 6).
Rauchhaus (2009) also attempts to test the effects of nuclear weapons possession on
conflict behavior. The data are generated using the EUGene (v.3.203) statistical package
for dyad years from 1885 through 2000 and for a subset period from 1946 through
2000.11 The findings indicate that, in militarized disputes, symmetric nuclear dyads have
a lower probability of war than do dyads where only one nation possesses nuclear arms.
Moreover, in dyads where there are nuclear weapons available on both sides (nuclear
pairs), the findings indicate that disputes are associated with higher probabilities of
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A study by Kroenig (2013) provides similar results. Using an original data set of 52
nuclear crisis dyads drawn from the International Crisis Behavior Project for the years
1945 through 2001, Kroenig codes the outcomes of nuclear crises against nuclear arsenal
size and delivery vehicles, and the balance of political stakes in the crisis. He concludes
“. . . that nuclear crises are competitions in risk taking, but that nuclear superiority—
defined as an advantage in the size of a state’s nuclear arsenal relative to that of its
opponent—increases the level of risk that a state is willing to run” (Kroenig, 2013, p.
143), and hence its probability of winning the dispute without violence. These results
support the contention that crises between nuclear-armed states tend to involve
dangerous tactics of brinkmanship and tests of resolve.
Evaluation
Evidence consistent with the risk manipulation, escalation, and limited war thesis would
include the presence of severe crises between nuclear powers that exhibit escalatory
behavior short of unconstrained war but inclusive of the use of force. The limited
conventional war of 1999 between India and Pakistan, initiated and carried out by
Pakistan under the umbrella of its nuclear deterrent, is an extreme example of precisely
this type of conflict interaction. It captures the logic of Snyder’s stability-instability
paradox and incorporates, as well, descriptions by Schelling and by Kahn of the use of
limited war (with the risk of greater violence to follow) as a means of persuading an
adversary to relinquish a contested value.
Beardsley and Asal (2009A) report that symmetric nuclear dyads engage in an
unexpectedly large number of crises—a finding that is consistent with the Snyder and
Diesing (1977) contention that crises have become surrogates for war among nuclear-
armed states. Similarly, Huth, Bennett, and Gelpi (1992) note that, in great-power dyads,
the possession of nuclear weapons by the defender does not deter dispute initiation by a
nuclear-armed challenger, and that an outcome of either war or capitulation by the
defender is unlikely. In findings not inconsistent with those of Huth et al., (1992), Kugler
(1984) reports that (between 1946 and 1981), as the capacity of nuclear actors to destroy
each other increases, there is a tendency to decrease the intensity of the conflict. Both
Geller (1990) and Rauchhaus (2009), in large-scale quantitative empirical analyses of
escalation patterns in nuclear, nonnuclear, and mixed (asymmetric) dyads, report that
symmetric nuclear dyads are substantially more likely to escalate dispute hostility levels
—short of war—than are nonnuclear pairs of states. In Geller’s study, the findings indicate
that disputes in which both parties possessed nuclear weapons had approximately a
seven times greater probability of escalation (0.238) than did disputes in which neither
party possessed nuclear arms (0.032). Last, Kroenig (2013) demonstrates that
confrontations between nuclear-armed states may be understood as competitions in risk
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These cumulative findings are strongly supportive of the risk manipulation, escalation,
and limited war thesis on the effects of symmetric nuclear weapons possession.12
Moreover, the case of the 1999 limited conventional war between India and Pakistan
reflects both the logic of this school of thought as well as the patterns of escalation
described in the large-scale quantitative studies of militarized disputes between nuclear-
armed states.
Nuclear Irrelevance
Theory
The views of John Mueller are most commonly associated with the thesis of “nuclear
irrelevance.” Mueller (1988, 1989) makes the highly controversial argument that nuclear
weapons neither defined the stability of the post-Second World War U.S.-Soviet
relationship nor prevented a war between the superpowers; he also maintains that the
weapons did not determine alliance patterns or induce caution in U.S.-Soviet crisis
behavior. His contention is that the postwar world would have developed in the same
manner even if nuclear weapons did not exist.
Mueller’s logic allows that a nuclear war would be catastrophic, but that nuclear weapons
simply reinforced a military reality that had been made all too clear by World War II: even
conventional war between great powers is too destructive to serve any conceivable
political purpose. Moreover, the satisfaction with the status quo shared by the United
States and the Soviet Union removed any desire for territorial conquest that might have
led to conflict, as each superpower held dominance in its respective sphere of influence.
Similarly, provocative crisis behavior was restrained by the fear of escalation—and
although the presence of nuclear weapons may have embellished such caution, the mere
possibility of fighting another conventional war such as World War II would have induced
fear and restraint on the part of decision makers. In short, nuclear weapons may have
enhanced Cold War stability, but their absence would not have produced a different
world. Mueller closes his argument with the extrapolation that war among developed
nations is obsolescent. It may simply be that, in the developed world, a conviction has
grown that war among post-industrial states “would be intolerably costly, unwise, futile,
and debased” (Mueller, 1988, p. 78). In this sense, nuclear weapons lack deterrent value
among developed states because—absent the incentive for war—there is nothing to deter.
In a related thesis, Vasquez (1991) holds that it is unlikely—given what is known about
the complex conjunction of multiple factors in the steps to war—that any single factor,
such as the availability of nuclear weapons, causes or prevents wars. He makes the
nuanced argument, in discussing the long post-war peace between the United States and
the Soviet Union, that:
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A second area of application for the nuclear irrelevancy thesis involves asymmetric dyads.
Little has been written about the effects of nuclear weapons on the patterns of serious
disputes where this technology is possessed by only one side. However, what has been
written suggests that in these types of conflicts nuclear weaponry may lack both military
and psychological salience. For example, Osgood and Tucker (1967, p. 158) and Blainey
(1973, p. 201) argue that tactical nuclear weapons are largely devoid of military
significance in either Third World conflicts or insurgencies, where suitable targets for the
weapons are absent. An additional disincentive to the use of nuclear weapons against a
nonnuclear opponent is that it might be expected to increase the pressures for nuclear
proliferation and to incite international criticism and denunciation of the nuclear state
(Huth, 1988A, p. 428). It also has been suggested that a sense of fairness or
proportionality contributes a moral aspect to the practical military and political
inhibitions on using nuclear weapons against a nonnuclear opponent and that the set of
these concerns has undermined the efficacy of nuclear power as a deterrent in
asymmetric conflicts (Huth & Russett, 1988, p. 38; Russett, 1989, p. 184).
Moreover, Waltz (1967, p. 222) and Osgood and Tucker (1967, pp. 162–163) caution
against exaggerating the differences due to nuclear weapons between contemporary and
historical major power-minor power conflicts. Long before the advent of nuclear weapons,
minor powers frequently defied or withstood great power pressure as a result of
circumstances of geography, alliance, or an intensity of interests that the major power
could not match.
In a similar argument, Jervis (1984, p. 132) examines the logic of escalation in a losing
cause (presumably a tactic relating directly to disputes between nuclear and nonnuclear
states) and suggests that a threat to fight a war that almost certainly would be lost may
not be without credibility—indeed, there may be compelling reasons for actually engaging
in such a conflict. Specifically, if the cost of winning the war is higher to the major power
than is the value at stake in the dispute, then the confrontation embodies the game
structure of “Chicken.” Hence, even if war is more damaging to the minor power than to
the major power, the stronger may still prefer capitulation or a compromise solution to
the confrontation rather than engaging in the fight. In sum, Jervis (1984, p. 135) argues
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The third area of application for the nuclear irrelevancy thesis involves policies of
extended deterrence. The efficacy of nuclear weapons for the purposes of extended
deterrence was an issue of immense importance throughout the Cold War. In fact, the
positions on whether American strategic nuclear weapons were sufficient to deter a
Soviet-Warsaw Pact invasion of Western Europe or whether substantial conventional and
tactical nuclear weapons were necessary for successful deterrence constituted a
continuing debate for decades. Nuclear revolution theory contended that the U.S.
strategic nuclear arsenal (with its ability to destroy the Soviet Union) was sufficient to
induce caution and restraint on the part of the Soviet leadership. However, the strategists
who formulated the stability-instability paradox argued that U.S. strategic nuclear
weapons would deter a direct nuclear strike on the United States itself, but little else.
According to this logic, for the successful extended deterrence of an attack on Europe,
the United States and NATO required effective combat forces that could fight at the level
of conventional war and even war with tactical nuclear weapons. Escalation dominance
was required to sustain extended deterrence. Of course, extended deterrence policies
existed long before the development of nuclear weapons and applied to any situation
where a powerful defender attempted to deter an attack against an ally by threat of
military response. The issue at hand is the effectiveness of a strategic nuclear threat in
sustaining a successful extended deterrence policy. The nuclear irrelevancy position is
that such weapons lack significance in extended deterrence situations.
In sum, the nuclear irrelevance thesis suggests that nuclear weapons have little salience
in the interaction patterns of nuclear-armed dyads. Evidence consistent with this position
would indicate that, for symmetric dyads, the possession of nuclear weapons or the
nuclear balance does not affect crisis escalation, crisis outcomes, or dispute initiation
patterns. In addition, if a set of practical, political, and ethical constraints has weakened
the military advantage of possessing nuclear weapons in a serious dispute with a
nonnuclear state, then the monopolization of a nuclear capability will not confer a
bargaining edge to the nuclear-armed state in an asymmetric crisis. The nuclear
irrelevance school would also gain support in findings indicating the absence of
substantive effects resulting from possession of nuclear weapons in extended deterrence
situations.
Empirical Evidence
In evaluating the empirical evidence regarding the nuclear irrelevance thesis, it is useful
analytically to separate the studies into distinct categories: (a) findings involving the
effects of nuclear weapons in nuclear-armed dyads; (b) findings involving the interaction
patterns of nuclear-armed states against nonnuclear opponents; and (c) findings bearing
on extended deterrence situations.
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However, other evidence relating to conflict behavior, crisis interaction patterns, or crisis
outcomes that indicate that nuclear weapons were inconsequential in the disputes would
support the contention that nuclear forces are irrelevant in symmetric dyads. For
example, Blechman and Kaplan (1978) provide an empirical analysis of 215 incidents
between 1946 and 1975, in which the United States used its armed forces for political
objectives. Their findings indicate that the strategic nuclear weapons balance between
the United States and the Soviet Union did not influence the outcome of competitive
incidents involving the two states (Blechman & Kaplan, 1978, pp. 127–129). Instead, the
authors maintain that the local balance of conventional military power was more
important in determining the outcomes of the confrontations (Blechman & Kaplan, 1978,
p. 527).
In contrast to the findings by Blechman and Kaplan (1978) and Kugler (1984), a study by
Kroenig (2013) provides different results. Using a data set of 52 nuclear crisis dyads
(1945–2001) drawn from the International Crisis Behavior (ICB) Project, Kroenig codes
the outcomes of nuclear crises, nuclear arsenal size and delivery vehicles, and the
balance of political stakes in the crisis. He concludes that nuclear superiority—defined as
an advantage in the size of a state’s nuclear arsenal relative to that of its opponent—
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Huth et al. (1992) examine militarized dispute-initiation patterns among great power
rivalries between 1816 and 1975 as a means of testing a set of explanatory variables
drawn from multiple levels of analysis. The principal focus of the study is to investigate
the relationship between the structure of the international system and the initiation of
great power disputes. However, the analysis does include a variable coded for the
possession of nuclear weapons by the challenger’s rival. The findings indicate that the
presence of defenders’ nuclear weapons does not deter challengers from initiating
militarized disputes among great powers (Huth et al., 1992, p. 478, 513).
Gartzke and Jo (2009) examine the effects of nuclear weapons possession on patterns of
militarized dispute initiation using a sophisticated multivariate model and data drawn
from the COW/MID database for directed dyads over the years 1946 through 2001. Their
findings indicate that nuclear weapons possession has little effect on dispute initiation
behavior. The authors note that: “Instead, countries with security problems, greater
interest in international affairs, or significant military capabilities are simultaneously
more likely to fight and proliferate” (Gartzke & Jo, 2009, p. 221). The relationship
between nuclear weapons and MID initiation is rejected statistically: this finding applies
to both symmetric (nuclear) and asymmetric (nuclear/nonnuclear) dyads.
(b) Asymmetric dyads. The nuclear irrelevancy school also maintains that the
possession of nuclear weapons confers no bargaining advantage on the nuclear-armed
power engaged in a confrontation with a nonnuclear state.
In a related study, Kugler (1984) isolates 14 cases of extreme crisis that occurred
between 1946 and 1981, in which nuclear weapons were available to at least one party in
the dispute. Of these 14 cases, nine involved confrontations in which only one state had
access to nuclear arms. In all nine cases, the outcomes of the crises favored the
nonnuclear challenger. Once again, the balance of conventional military capabilities—not
nuclear weaponry—provided the best predictor of crisis outcome (Kugler, 1984, p. 501).
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In two studies published in 1994 and 1995, Paul employs the case study method to
examine the dynamics of asymmetric war initiation by weaker powers. Paul (1994)
analyzes six cases of war initiation by weaker states against stronger states: three of
these cases (China/U.S. in 1950; Egypt/Israel in 1973; and Argentina/Great Britain in
1982) involve nonnuclear nations initiating wars against nuclear-armed opponents. Paul
(1994, p. 173) concludes that nuclear weapons appear to have limited utility in averting
war in asymmetric dyads. He notes that, with either nuclear or conventional weapons, a
significant military advantage may be insufficient to deter a weaker state that is highly
motivated to change the status quo. In a more focused study, Paul (1995) discusses the
possible reasons underlying the nonuse of nuclear weapons by nuclear-armed states
against nonnuclear opponents. Here he analyzes two cases (Argentina/Great Britain in
the Falklands War of 1982 and Egypt/Israel in the Middle East War of 1973) in which
nonnuclear states initiated wars against nuclear opponents. Paul argues that in both
cases nuclear retaliation by the targets was deemed highly improbable by the nonnuclear
war initiators due to a combination of limited war goals and taboos (unwritten and
uncodified prohibitionary norms) against the use of nuclear weapons.
Rauchhaus (2009) attempts to test the effects of nuclear weapons possession on conflict
behavior for asymmetric as well as for symmetric dyads using data generated by the
EUGene (v.3.203) statistical program for dyad years from 1885 through 2000. The
findings indicate that, for asymmetric (nuclear/nonnuclear) dyads (in comparison to
symmetric dyads), there is a higher probability of war. Asymmetric dyads are also more
likely to be involved in militarized disputes that reach the level of the use of force
(Rauchhaus, 2009, pp. 269–270). In short, the study produces results that hold in
opposition to the view that conflict between nuclear and nonnuclear states will be limited.
As Rauchhaus (2009, p. 271) concludes: “nuclear asymmetry is generally associated with
a higher chance of crises, uses of force, fatalities, and war.”
A study by Beardsley and Asal (2009B) produces findings that stand in counterpoint to
the main body of analyses on conflict in asymmetric dyads. This work examines the
question of whether the possession of nuclear weapons affects the probability of
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However, with regard to bargaining advantages that may be derived from the possession
of nuclear weapons, Sechser and Fuhrmann (2013) argue (counter to Beardsley & Asal)
that compellent threats based on nuclear force may lack credibility due to their
indiscriminately destructive effects and the reputational costs that, presumably, would be
associated with their use. Drawing on a new data set (Militarized Compellent Threats)
containing 242 challenger-target dyads for the period 1918 to 2001, they report findings
indicating that “states possessing nuclear weapons are not more likely to make successful
compellent threats [than nonnuclear states] . . . and that nuclear weapons carry little
weight as tools of compellence” (Sechser & Fuhrmann, 2013, p. 174).
(c) Extended deterrence. The logic of the nuclear irrelevancy thesis suggests that
nuclear weapons should be of little salience in extended deterrence situations.
Huth defines deterrence as a policy that seeks to convince an adversary through threat of
military retaliation that the costs of using military force outweigh any expected benefits.
Extended deterrence is then defined by Huth (1988A, p. 424) as a confrontation between
a defender and a potential attacker in which the defender threatens the use of military
force against the potential attacker’s use of force against an ally (protégé) of the
defender. There have been a large number of studies produced on the issue of the efficacy
of extended nuclear deterrence—the majority of which report a body of consistent or
complementary findings.
As noted in Harvey and James (1992), Bruce Russett’s (1963) analysis of 17 crises that
occurred between 1935 and 1961 appears to be the first aggregate study of the factors
associated with extended deterrence success and failure. Nine crisis cases involved
defenders with a nuclear capability, and six of the nine cases resulted in successful
extended deterrence. However, Russett draws no conclusions as to the independent effect
of nuclear weapons on those outcomes. He does note that military equality on either the
local (conventional) or strategic (nuclear) level appears to be a necessary condition for
extended deterrence success.
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In a subsequent study, Huth and Russett (1984) increased the size of Russett’s (1963)
sample set from 17 to 54 historical cases of extended deterrence from 1900 through
1980. The findings indicate that the effect of nuclear weapons on extended deterrence
success or failure is marginal. Of much greater import are the combined local
conventional military capabilities of the defender and protégé; hence, conventional,
rather than nuclear, combat power is associated with the probability of extended
deterrence success.
In two related studies, Huth (1988A, 1988B) examines 58 historical cases of extended
deterrence and reports findings similar to those found in Huth and Russett (1984).
Specifically, the possession of nuclear weapons by the defender did not have a
statistically significant effect on deterrence outcomes when the target itself was a
nonnuclear power. In addition, the ability of the defender to deny the potential attacker a
quick and decisive conventional military victory on the battlefield was correlated with
extended deterrence success.
Huth and Russett (1988) present an analysis of Huth’s (1988B) 58 historical cases of
extended deterrence success and failure. In this database, there were 16 cases of
extended deterrence crises where defenders possessed nuclear weapons. The findings
indicate that a defender’s nuclear capability was essentially irrelevant to extended
deterrence outcomes; existing and locally superior conventional military forces were of
much greater importance to deterrence success.
Huth (1990) produced another study based on the data set described in his 1988b book.
In this study, he examines the effects of the possession of nuclear weapons by a defender
only in extended deterrent crises not characterized by mutual assured destruction (i.e.,
where the potential attacker either does not possess nuclear weapons or does not possess
a significant nuclear capability). He reports that, when the defender has an advantage in
conventional forces, nuclear weapons do not play a significant role in the outcomes of
extended deterrence confrontations (Huth, 1990, p. 271).
Fuhrmann and Sechser (2014) report findings similar to those of Weede (1981, 1983) and
Carlson (1998), insofar as the independent extended deterrent effect of nuclear weapons
is supported. Using Militarized Interstate Dispute (MID) data for the years 1950 through
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Evaluation
The empirical evidence regarding the nuclear irrelevance thesis has been divided
analytically into three distinct categories: (a) findings involving the effect of nuclear
weapons in nuclear dyads; (b) findings involving the interaction patterns of nuclear-
armed states against nonnuclear opponents; and (c) findings relating to extended
deterrence situations.
Nevertheless, there is a body of evidence for nuclear dyads that supports the nuclear
irrelevancy thesis; these findings focus on the effects of the nuclear balance on crisis
outcomes and the effect of nuclear weapons on patterns of dispute initiation. Both
Blechman and Kaplan (1978; with 215 incidents from 1946 to 1975) and Kugler (1984;
five extreme crises between 1946 and 1981), report that the balance of nuclear forces in
nuclear dyads was less significant in influencing the outcome of confrontations than was
the local balance of conventional military capabilities. Only Kroenig’s (2013) work
indicates a crisis bargaining advantage accruing to a state with nuclear superiority in
symmetric nuclear dyads. With regard to dispute initiation, Huth et al. (1992) report a
lack of salience regarding the availability of nuclear weapons for great powers and the
initiation patterns of their militarized disputes. Gartzke and Jo (2009) similarly note that
nuclear weapons show no statistically significant relationship to the initiation of
militarized interstate disputes in either symmetric or asymmetric dyads. In sum, the
findings of this subset of studies are consistent with the thrust of the nuclear irrelevancy
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Geller’s (1990) analysis indicates that in 34 asymmetric disputes with a nuclear initiator,
the nonnuclear target matched or escalated the initiator’s hostility level in 24 cases
(71%); in 56 asymmetric disputes with a nonnuclear initiator, the nuclear target
deescalated the crisis by failing to match or exceed the nonnuclear initiator’s hostility
level in 35 cases (63%). Moreover, 35 of the total of 90 cases (39%) of asymmetric
disputes reached the level in which force was used. These findings show that in this class
of dyad, nonnuclear dispute initiators as well as targets act more aggressively than do
their nuclear-armed opponents. The conclusion suggests that in confrontations between
nuclear and nonnuclear states, the use of force, including war, is a distinct possibility,
with aggressive escalation by the nonnuclear state probable. In such cases of asymmetric
distribution of nuclear forces, the conventional military balance may well be the
determinative factor in the outcome of the dispute.
The findings of Rauchhaus (2009) reinforce those discussed above: there is a higher
probability of war in asymmetric dyads than in symmetric nuclear dyads, and asymmetric
dyads are more likely than symmetric nuclear dyads to experience militarized disputes
that engage the use of force. As Rauchhaus concludes, nuclear asymmetry is associated
with higher probabilities of crises, limited use of force, and war, than are symmetric
nuclear dyads.
A study by Narang (2013) offers corollary evidence that the deterrent effect of the
possession of nuclear weapons (for regional nuclear powers engaged in disputes with
nonnuclear states) depends heavily on the nuclear posture that is adopted. Specifically, in
contrast to catalytic or assured destruction postures, only an asymmetric escalation
posture has any effect in deterring conventional military assaults. Last, Sechser and
Fuhrmann (2013) report findings indicating that, although nuclear weapons may provide
deterrent value, they are irrelevant as instruments of compellence.
These results are generally consistent with the predictions of the nuclear irrelevance
thesis regarding conflict patterns in asymmetric dyads: the possession of nuclear
weapons confers little or no advantage to nuclear-armed states in disputes with
nonnuclear opponents. Paul’s (1994, 1995) case studies of instances of war initiation by
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In sum, the findings of this subset of studies are supportive of the thrust of the nuclear
irrelevance thesis regarding both the effects of the nuclear balance on crisis outcomes
and the effects of nuclear weapons possession on dispute initiation patterns: the
possession of nuclear weapons does not impede aggressive behavior by nonnuclear
states.
In sum, the cumulative findings in all three areas are consistent with some of the
predictions of the nuclear irrelevance school and inconsistent with others. For symmetric
nuclear dyads, a substantial set of findings indicates that patterns of war and crisis
escalation differ between symmetric nuclear dyads, asymmetric dyads, and nonnuclear
dyads. Counter to the predictions of the nuclear irrelevancy thesis, nuclear weapons
affect the nature of conflict interaction between nuclear-armed states. At the same time,
there is a subset of findings consistent with the predictions of nuclear irrelevancy for
nuclear dyads: the nuclear balance does not affect the outcome of crises (the balance of
local conventional military forces is more important), nor does the symmetric possession
of nuclear weapons distinguish initiation patterns of militarized disputes from initiation
patterns in asymmetric or nonnuclear disputes. Also supportive of the irrelevancy thesis
are findings indicating that, for asymmetric dyads, the possession of nuclear arms
provides scant advantage in crises and confrontations with nonnuclear states. Escalation
by the nonnuclear adversary and its use of force—including war—are outcomes with
surprisingly high probabilities. Last, in extended deterrence situations, the cumulative
findings tend toward the essential irrelevance of nuclear weapons possession and point
instead toward the salience of the local balance of conventional military forces in
determining crisis outcomes.
Conclusion
This article has reviewed the three principal schools of thought regarding the effects of
nuclear weapons possession on patterns of international conflict: (a) nuclear revolution
theory; (b) risk manipulation, escalation, and limited war; and (c) nuclear irrelevance.
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For nuclear revolution theory, the findings offer limited, but not insignificant, support. For
example, as predicted, wars among nuclear-armed states have been rare events. To date,
with the exception of India and Pakistan in 1999, no other militarized dispute between
nuclear powers has reached the level of war (based on Correlates of War Project coding
rules). As Waltz and Jervis have predicted, wars occur among nuclear-armed states at a
far lower proportional frequency than in asymmetric or nonnuclear dyads. However, the
prediction of nuclear revolution theory—that there will be few crises among nuclear-
armed powers—has not been supported by the quantitative empirical evidence. Similarly,
the prediction that those crises that do develop among nuclear powers will be settled
rapidly and without serious escalation has not found empirical support.
For the risk manipulation, escalation, and limited war school, the evidence has proved
more uniformly favorable. The prediction by Snyder and Diesing (1977) that crises among
nuclear-armed states will be used as surrogates for war—with associated tactics
(including the limited use of force) designed to increase risk and intimidate through
dangerous escalatory behaviors—has been largely supported. Comparisons of crisis
escalation probabilities between symmetric nuclear dyads, asymmetric dyads, and
nonnuclear dyads clearly show higher escalation probabilities for nuclear dyads than for
the other two classes, with disputes for nuclear dyads approximately seven times more
likely to escalate—short of war—than disputes for nonnuclear dyads. Moreover, the case
of the 1999 war between India and Pakistan conforms to the logic of Snyder’s stability-
instability paradox whereby limited war is fought between nuclear powers under the
protective umbrellas of their nuclear deterrents.
The nuclear irrelevance school, like nuclear revolution theory, finds mixed support in the
extant empirical evidence. The nuclear irrelevancy thesis can be categorized according to
predictions involving (a) the effects of nuclear weapons in nuclear dyads, (b) the effects
of nuclear weapons possession in asymmetric dyads, and (c) the effects of nuclear
weapons in extended deterrence situations. Counter to the logic of this school,
cumulative empirical evidence indicates that nuclear weapons do make a difference in
certain types of conflict interaction. Patterns of war and crisis escalation differ between
symmetric nuclear dyads, asymmetric dyads, and nonnuclear dyads, with nuclear dyads
less likely to fight wars and more likely to exhibit crisis escalation patterns short of war
than nonnuclear dyads.
Supportive of the contentions of the nuclear irrelevancy school are findings indicating
that in asymmetric dyads, the possession of nuclear arms provides no discernable
advantage in crises and confrontations. Escalation by the nonnuclear adversary and its
use of force against its nuclear-armed opponent—including war—are distinct outcomes
with surprisingly high probabilities. Lastly, in extended deterrence situations, the
cumulative findings indicate the essential irrelevance of nuclear weapons possession and
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Acknowledgment
I wish to thank John Vasquez, Jack Levy, and Peter Wallensteen for their expert
commentaries on an earlier version of this article. This article is an expanded and revised
version of Daniel S. Geller (2012), Nuclear Weapons and War, in J. A. Vasquez (Ed.), What
Do We Know About War? (2d ed.). Used by permission of Rowman & Littlefield Publishing
Group. All rights reserved.
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Notes:
(1.) See Gartzke and Kroenig (2016) for an excellent review of this literature. Related
studies that examine the determinants of nuclear proliferation include Meyer (1984),
Sagan (1996/1997), Geller (2003), Singh and Way (2004), Hymans (2006, 2012), Solingen
(2007, 2012), Jo and Gartzke (2007), Gartzke and Kroenig (2009), Kroenig (2009, 2010),
Fuhrmann (2009), Horowitz (2010), Bleek (2010), Bleek and Lorber (2014), Brown and
Kaplow (2014), Miller (2014), Way and Weeks (2014), and Reiter (2014).
(2.) As Mueller (1988, pp. 55–56) notes: “nuclear weapons neither define a fundamental
stability nor threaten severely to disturb it. . . [W]hile nuclear weapons may have
substantially influenced political rhetoric, public discourse, and defense budgets and
planning, it is not at all clear that they have had a significant impact on the history of
world affairs since World War II.”
(3.) Others attributing to nuclear weapons causal significance for the “long peace”
between the United States and the Soviet Union include The Harvard Nuclear Study
Group (1983), Tucker (1985), Quester (1986), Bundy (1988), and Gaddis (1991). However,
Levy (1989, pp. 289–295), while noting the stability in the superpower relationship
produced by nuclear weapons, cautions about pressures for preemptive war that may
develop between nuclear-armed states.
(4.) Intriligator and Brito (1981) present a similar formal mathematical analysis of the
effects of nuclear proliferation on the probability of nuclear war—but in this case without
associated empirical data. The mathematical model demonstrates that the effects of
nuclear proliferation on the probability of nuclear war depend on the number of existing
nuclear weapon states, and that proliferation may reduce rather than increase the
probability of nuclear war. Once two or more states achieve a secure second-strike
capability, the addition of new nuclear states decreases the incentive to initiate a nuclear
war. However, Intriligator and Brito note that, while the probability of a calculated
nuclear attack may decrease as a result of proliferation, there may be an increase in the
probability of accidental or irrational nuclear war as these weapons spread throughout
the system.
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(6.) Major works, many using formal mathematical models, that explore the factors
associated with deterrence, brinkmanship and the manipulation of risk, crisis stability,
threat credibility, and the consequences of nuclear proliferation include those by Ellsberg
(1959[1968], 1960), Brams and Kilgour (1985), Powell (1987, 1988), Kugler (1987),
Nalebuff (1988), Langlois (1991), Wagner (1991), Carlson (1995), Brito and Intriligator
(1996), Zagare and Kilgour (2000), Danilovic (2002), Morgan (1977, 2003), and Zagare
(2007).
(7.) For example, see Bundy and Blight (1987–1988, pp. 30–92). Glaser and Fetter (2016),
in a sophisticated analysis of potential United States damage-limitation strategies and
forces vis-à-vis China, conclude that such an effort would most likely fail and would
undermine a stable deterrence relationship. Indeed, Mueller (1988, 1989) presents an
argument that, among developed countries, major war (nuclear or conventional) is no
longer considered a realistic foreign policy option due to the massive destructive effects.
But Mueller (1988, p. 56) also contends that nuclear weapons have not fundamentally
affected the crisis behavior of major powers. For a response to this argument, see Jervis
(1988).
(8.) Escalation theory is a subset of the more general body of theory on strategic
interaction in international politics (e.g., Singer, 1963).
(9.) Strategic theorists fully recognize, however, that escalation of conflict can occur
irrespective of the desires of the participants due to factors of miscalculation or
momentum. This possibility—and an appreciation of it—forms a key element in the work
of some theorists in this school (e.g., Schelling, 1966, chap. 3).
(10.) Other early works with sections on escalation that touch on the subject of risk are
Kahn (1962, chap. 6), Snyder (1961, pp. 252–258), Schelling (1966, pp. 99–116, 166–168),
Schelling (1960, appendix A), and Halperin (1963, chaps. 1–2, 4). The issue of “costly
signals” with regard to the credibility of threats and commitments are elaborations on the
themes of these early studies on escalation (e.g., Fearon, 1994a, 1994b, 1997; Schultz,
1998). For example, Fearon (1997, p. 82) discusses the relative merits of the “tie-hands”
and “sink-cost” signaling strategies. Fearon demonstrates (using formal methods) that
costly signals are more successful if they involve a tie-hands strategy (create costs that
would be paid ex post if they fail to uphold the commitment) rather than if a sink-cost
strategy is pursued (which is only costly to the actor ex ante). The tie-hands strategy is
connected to ex post domestic audience costs. The model also indicates that decision
makers will not bluff with either type of costly signal; they will not incur or create costs
and then fail to carry out the threat.
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(12.) In an interesting study at the monadic level, Grieco (2012) conducts a comparative
analysis of the conflict behavior of states before and after the acquisition of nuclear
weapons. His principal finding is that states do not become more prone to the initiation of
military crises after acquiring nuclear weapons.
(13.) In a more recent work, Vasquez (Senese & Vasquez, 2008) allows that nuclear
weapons have raised the provocation threshold for total war: “What would have provoked
a war between major states in the pre-nuclear era no longer does so” (Senese & Vasquez,
2008, p. 62). Nevertheless, Vasquez (2009) continues to maintain that a proper evaluation
of the effects of nuclear weapons on war is within the context of the “steps to war” model
(e.g., Senese & Vasquez, 2008; Vasquez, 1993). For an alternative explanation of war
based on a process of complex conjunctive causation see Geller and Singer (1998) and
Geller (2000b, 2004, 2005).
Daniel S. Geller
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