Japanese submarine I-63

Upon commissioning, I-63 was assigned to Submarine Division 28, in which she spent her entire career.[4] The division was assigned to the Sasebo Naval District on 24 December 1929,[4] then was reassigned to Submarine Squadron 2 in the 2nd Fleet in the Combined Fleet on 1 December 1930,[4] to Submarine Squadron 1 in the 1st Fleet in the Combined Fleet on 1 December 1932,[4] and to the Sasebo Defense Division in the Sasebo Naval District on 15 November 1933.[4] On 20 March 1934, I-63 was decommissioned and placed in reserve,[4] and while she was in reserve Submarine Division 28 was reassigned to the Sasebo Guard Squadron on 11 December 1933.[4]

Submarine Division 28 again was assigned to Submarine Squadron 2 in the 2nd Fleet on 15 November 1934, and I-63 was recommissioned that day.[4] On 7 February 1935 I-63 got underway from Sasebo along with the other five submarines of Submarine Squadron 2 — I-53, I-54 and I-55 of Submarine Division 18 and Submarine Division 28′s I-59 and I-60 — for a training cruise in the Kuril Islands.[4][5][6][7][8][9] The cruise concluded with their arrival at Sukumo Bay on 25 February 1935.[4][5][6][7][8][9] The six submarines got back underway from Sasebo on 29 March 1935 for a training cruise in Chinese waters and returned to Sasebo on 4 April 1935.[4][5][6][7][8][9] On 15 November 1935, Submarine Division 28 again was assigned to Submarine Squadron 1 in the 1st Fleet.[4]

On 27 March 1937, I-63 put to sea from Sasebo with I-59 and I-60 for a training cruise in the vicinity of Qingdao, China.[4][8][9] The three submarines concluded it with their arrival at Ariake Bay on 6 April 1937.[4][8][9] Submarine Division 28 was reassigned to the Sasebo Defense Squadron in the Sasebo Naval District on 1 December 1937[4] and then to Submarine Squadron 1 in the 1st Fleet on 15 December 1938.[4]

In January 1939, I-63 and the other submarines of Submarine Squadron 1 got underway for fleet exercises.[4] Early on the morning of 2 February 1939, the submarines were on their way to their assigned stations for a simulated attack against Japanese surface ships also taking part in the exercises.[10] I-63 arrived at her station in the Bungo Strait off Kyushu about 60 nautical miles (110 km; 69 mi) northwest of Mizunokojima Lighthouse and at 04:30 shut down her diesel engines and hove-to to await sunrise on the surface with all of her running lights on.[10]

I-60, proceeding on the surface at 12 knots (22 km/h; 14 mph) toward her own assigned station, mistakenly entered I-63′s assigned area due to a navigation error.[10] At around 05:00 I-60′s watch officer sighted two white lights belonging to I-63.[10] I-60′s lookouts misidentified I-63′s lights as those of two fishing boats in close proximity to one another.[10] I-60′s watch officer decided to pass between the supposed fishing boats,[10] unwittingly putting I-60 on a collision course with I-63. By the time I-60′s watch officer realized the lights belonged to I-63, the two submarines were only 220 yards (200 m) apart.[10] He ordered I-60 to turn in the hope of avoiding a collision.[10] Meanwhile, I-63′s crew called her commanding officer to her bridge, which he reached in time to see that I-60 was about to ram his submarine.[10] He issued a command for I-63 to go to all ahead full and ordered her crew to close all watertight doors.[10]

By the time the two submarines sighted each other, it was too late to avoid a collision, and I-60 rammed I-63.[4][10][11][12] The impact tore open I-63′s starboard ballast tank and auxiliary machinery compartment.[10] I-63 sank in a few minutes in 320 feet (98 m) of water with the loss of 81 members of her crew.[4][10][11] I-60, which had suffered a crushed bow buoyancy tank, rescued I-63′s commanding officer and six other crewmen.[10] They were I-63′s only survivors.[4][10][11]

As the result of the post-accident investigation, a court of inquiry found that I-60′s navigation error had contributed to the accident and that I-60 had unsatisfactory lookout procedures and inadequate management of her watch officers.[10] Although off the bridge and below at the time of the collision, I-60′s commanding officer took full responsibility for the accident.[10] After a trial by court-martial, he was suspended from duty, and his later promotion from lieutenant commander to commander was delayed.[10]