Japanese submarine Ro-63

The submarines of the Type L4 sub-class were copies of the Group 3 subclass of the British L-class submarine built under license in Japan.^[1] They were slightly larger and had two more torpedo tubes than the preceding submarines of the L3 subclass.^[1] They displaced 1,004 tonnes (988 long tons) surfaced and 1,322 tonnes (1,301 long tons) submerged. The submarines were 78.39 meters (257 ft 2 in) long and had a beam of 7.41 meters (24 ft 4 in) and a draft of 3.96 meters (13 ft 0 in). They had a diving depth of 60 meters (197 ft).

For surface running, the submarines were powered by two 1,200-brake-horsepower (895 kW) Vickers diesel engines, each driving one propeller shaft. When submerged, each propeller was driven by an 800-shaft-horsepower (597 kW) electric motor. They could reach 15.7 knots (29.1 km/h; 18.1 mph) on the surface and 8.6 knots (15.9 km/h; 9.9 mph) underwater. On the surface, they had a range of 5,500 nautical miles (10,200 km; 6,300 mi) at 10 knots (19 km/h; 12 mph); submerged, they had a range of 80 nmi (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph).

The submarines were armed with six internal 533 mm (21 in) torpedo tubes, all in the bow, and carried a total of twelve 6th Year Type torpedoes. They were also armed with a single 76.2 mm (3 in) deck gun and a 6.5 mm machine gun.

Ro-63 was laid down as Submarine No. 84 on 2 April 1923 by Mitsubishi at Kobe, Japan.^[2][3] Launched on 24 January 1924,^[2][3] she was renamed Ro-63 on 1 November 1924 while fitting out.^[2][3] She was completed and commissioned on 20 December 1924.^[2][3]

Upon commissioning, Ro-63 was attached to the Maizuru Naval District and assigned to Submarine Division 33.^[2] On 1 June 1925, she was transferred to the Sasebo Naval District and reassigned to Submarine Division 24, in which she remained until 1939.^[2] Submarine Division 24 was reassigned to Submarine Squadron 1 in the 1st Fleet in the Combined Fleet on 1 December 1925.^[2] On 1 March 1926, Ro-63 and the submarines Ro-57, Ro-58, Ro-59, Ro-60, Ro-61, Ro-62, Ro-64, and Ro-68 departed Sasebo, Japan, bound for Okinawa, which they reached the same day.^{[2][4][5][6][7][8][9][10][11]} The nine submarines got underway from Okinawa on 30 March 1926 for a training cruise in Chinese waters off Shanghai and Amoy which concluded with their arrival at Mako in the Pescadores Islands on 5 April 1926.^{[2][4][5][6][7][8][9][10][11]} They departed Mako on 20 April 1926 for the return leg of their training cruise, operating off China near Chusan Island, then returned to Sasebo on 26 April 1926.^{[2][4][5][6][7][8][9][10][11]} On 27 March 1927, Ro-60, Ro-61, Ro-62, Ro-63, Ro-64, and Ro-68 departed Saeki Bay, Japan, for a training cruise off Qingdao, China, which they concluded with their arrival at Sasebo, Japan, on 16 May 1927.^{[2][7][8][9][10][11]}

On 10 December 1928, Submarine Division 24 was transferred back to the Sasebo Naval District and began service in the Sasebo Defense Division.^[2] Ro-63 was decommissioned on 10 March 1929 and placed in reserve at Maizuru,^[2][3] but was recommissioned on 29 June 1929.^[2] While proceeding to Sasebo, Japan, on 13 November 1929 after conducting diving exercises with Ro-64, Ro-63 collided off Sasebo with the small Japanese motor vessel Segawa Maru, suffering minor damage to her starboard bow.^[3]

Submarine Division 24 returned to duty in Submarine Squadron 1 in the 1st Fleet on 30 November 1929.^[2] It transferred back to the Sasebo Naval District on 1 December 1930^[2] and began a stint in the Sasebo Defense Division on 1 December 1931.^[2] Ro-63 again was decommissioned on 1 December 1932 and placed in reserve at Maizuru.^[2][3]

Ro-63 was recommissioned on 20 March 1934,^[2] resuming active service in Submarine Division 24, which by then was assigned to the Sasebo Guard Squadron in the Sasebo Naval District.^[2] The division′s service in the Sasebo Guard Squadron ended on 15 November 1934, after which it was assigned directly to the Sasebo Naval District until 1 December 1936, when it was assigned to the Sasebo Defense Squadron.^[2] It resumed its direct assignment to the Sasebo Naval District on 1 January 1938.^[2]

Ro-63 was transferred to Submarine Division 33 on either 1 September^[3] or 15 November 1938,^[2] according to different sources, for service at the submarine school at Kure, Japan.^[2] On 15 November 1939, Submarine Division 33 was reassigned to Submarine Squadron 7 in the 4th Fleet in the Combined Fleet.^[2] When the Imperial Japanese Navy deployed for the upcoming conflict in the Pacific, Ro-63 was at Kwajalein in the Marshall Islands.^[3] She received the message "Climb Mount Niitaka 1208" (Japanese: Niitakayama nobore 1208) from the Combined Fleet on 2 December 1941, indicating that war with the Allies would commence on 8 December 1941 Japan time,^[3] which was on 7 December 1941 on the other side of the International Date Line in Hawaii, where Japanese plans called for the war to open with their attack on Pearl Harbor.

Ro-63 was with the other submarines of Submarine Division 33 — Ro-64 and Ro-68 — at Kwajalein when Japan entered World War II on 8 December 1941, Kwajalein time.^[3] That day, she got underway to conduct a reconnaissance of Howland Island.^[3] She sighted an enemy plane 85 nautical miles (157 km; 98 mi) northwest of Howland on 12 December,^[3] reconnoitered Howland on 14 and 15 December,^[3] and returned to Kwajalein on 19 December 1941.^[3]

Ro-63 departed Kwajalein on 7 January 1942 and called at Truk in the Caroline Islands from 11 to 15 January before getting back underway in company with Ro-64 and Ro-68 to conduct a reconnaissance of Rabaul on New Britain in the Admiralty Islands.^[3] She then patrolled south of Cape St. George on New Ireland before returning to Truk on 29 January 1942.^[3]

Ro-63, Ro-64, and Ro-68 left Truk on 18 February 1942, called at Ponape from 23 to 24 February, and then set out for the Marshall Islands area.^[3] During their voyage, however, Ro-63′s horizontal rudder failed on 27 February 1942, and she proceeded to Bikini Atoll for repairs in company with Ro-64.^[3][12] The two submarines reached Bikini on 28 February 1942.^[12] They got back underway on 1 March 1942, but Ro-63′s jury-rigged rudder quickly broke again and she turned back to Bikini while Ro-64 proceeded independently.^[3][12] On 2 March 1942, she departed Bikini^[3] to head for Japan for repairs, calling along the way at Ponape from 5 to 7 March 1942,^[3] at Truk from 9 to 19 March 1942,^[3] and at Saipan in the Mariana Islands from 22 to 26 March 1942^[3] before arriving at Maizuru on 3 April 1942.^[3]

After her repairs were completed, Ro-63 departed Maizuru on 5 June 1942,^[3] arrived at Saipan on 13 June, and then made for Truk.^[3] Recalled to Japan, she departed Truk on 27 June 1942^[3] bound for Yokosuka, Japan, which she reached on 4 July 1942.^[3]

On 14 July 1942, Submarine Division 33 was reassigned to the 5th Fleet^[3] for service in the Aleutian Islands, where the Aleutian Islands campaign had begun in June 1942 with the Japanese occupation of Attu and Kiska. At 16:00 on 24 July 1942, Ro-63, Ro-64, and Ro-68 departed Yokosuka bound for Paramushiro in the northern Kurile Islands.^[3] Ro-64 was forced to return to Yokosuka when food poisoning broke out among her crew,^[12] but Ro-63 and Ro-68 pressed on and arrived at Paramushiro on 29 July 1942.^[3] Ro-63 and Ro-68 put to sea again on 31 July 1942 to head for Kiska, which they reached on 4 August 1942.^[3] Thereafter, they were based there along with the submarines I-6, Ro-61, Ro-62, Ro-64, Ro-65, and Ro-67.^[3][13]

On 7 August 1942, an American task force bombarded Kiska while I-6, Ro-61, Ro-64, and Ro-68 were anchored in the harbor, and they crash-dived to avoid damage.^[13] Between 8 and 10 August 1942, Ro-61, Ro-63, Ro-64, and Ro-68 sought to intercept the American ships, but failed to find them.^[3] From 11 to 13 August 1942, Ro-63 participated with Ro-64 and Ro-68 in a search for the crew of a ditched reconnaissance plane,^[3][12][14] and Ro-63 subsequently conducted patrols off the Aleutians from her base at Kiska from 17 to 20 August, 28 to 30 August, 3 to 5 September, and 6 to 11 September 1942.^[3]

On 14 September 1942, Ro-63 was anchored at Kiska when American aircraft raided the base.^[3] She submerged to avoid attack, but a bomb a United States Army Air Forces Eleventh Air Force B-24 Liberator dropped nonetheless damaged one of her periscopes while she was underwater.^[3] Submarine Division 33 was attached directly to the 51st Base Unit at Kiska on 15 September 1942, and Ro-63 carried out another Aleutians patrol from 22 to 24 September 1942.^[3]

While Ro-63 was at Kiska on 25 September 1942, Submarine Division 33 was reassigned to the Kure Naval District.^[2] Ro-63, Ro-64, and Ro-68 departed Kiska on 26 September 1942 bound for Maizuru, where they arrived on 5 October 1942.^[3]

Ro-63 departed Maizuru on 6 November 1942 and arrived at Kure on 8 November 1942.^[3] Thereafter, Submarine Division 33 was assigned to training duties in the Kure Naval District.^[3] It was assigned to the Kure Submarine Squadron on 1 December 1943.^[3]

On 28 March 1945, Ro-63 was selected for conversion to a tender for Type D (Kōryū) midget submarines based on Amami Ōshima in the Amami Islands.^[3] After completion of a makeshift conversion at the Kure Naval Arsenal that included the installation of a Type 96 25 mm anti-aircraft gun and a radar detector,^[3] Ro-63 departed Kure on 8 April 1945, stopped at Sasebo, and then got underway from Sasebo on 10 April 1945 bound for Amami Ōshima.^[3] She arrived at Koniya on Amami Ōshima on 13 April 1945 and unloaded her cargo of torpedoes and spare parts.^[3] Continual Allied air attacks forced her to remain submerged on the harbor bottom at Koniya by day and surface only at night to perform her tender duties during darkness.^[3] On 29 April 1945, she received orders to return to Sasebo.^[3] After loading a cargo of sugar at Kasari Bay on Amami Ōshima on 30 April, Ro-63 headed for Sasebo, which she reached on 3 May 1945.^[3]

After her arrival at Sasebo, Ro-63 was drydocked until mid-May 1945,^[3] when she proceeded to Ōtake, Japan, to resume her training activities^[3] at the submarine school there. She was at Maizuru when hostilities between Japan and the Allies ended on 15 August 1945.^[3] She subsequently surrendered to Allied forces.^[3]

The Japanese struck Ro-63 from the Navy list on 20 November 1945.^[3] Allied forces scuttled her in the Iyo Nada in the Seto Inland Sea in May 1946.^[3]

• "Rekishi Gunzō"., History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005, ISBN 4-05-603890-2
• The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III, Ushio Shobō (Japan), September 1980, Book code 68343-44
• The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition", Ushio Shobō (Japan), February 1988, Book code 68344-36
• The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition", Ushio Shobō (Japan), March 1988, Book code 68344-37