I-12 was an Imperial Japanese Navy Type A2 long-range fleet submarine that served during World War II.

[3] For surface running, I-12 powered by two 4,700-brake-horsepower (3,505 kW) diesel engines, each driving one propeller shaft.

This allowed aircraft launching from I-12 to use the forward motion of the submarine to supplement the speed imparted by the catapult.

[6] Attached directly to 6th Fleet headquarters, she departed Kobe on 4 October 1944 for her first war patrol, ordered to attack shipping along the U.S. West Coast, in the Hawaiian Islands area, in the Tahiti area, and in the Pacific Ocean east of the Marshall Islands.

[6] During the early hours of 28 October 1944,[7] the American 7,176-gross register ton Liberty ship SS John A. Johnson — which had departed San Francisco, California, on 24 October with 41 crewmen, 28 United States Navy Armed Guard personnel, and a United States Army cargo security officer aboard bound for Honolulu, Territory of Hawaii,[8] with a cargo of crated and uncrated U.S. Army trucks on her deck and 6,900 tons of food and provisions[6][8] and 140[6] or 150[8] tons (according to different sources) of explosives in her holds[6] — broke radio silence for 12 minutes to report the loss overboard in heavy seas of a life raft, a common practice in peacetime to avoid unnecessary search-and-rescue operations if the raft was found, despite the suspension of such reports during World War II due to the wartime proliferation of rafts and wreckage and the need to maintain communications security.

[9] At 21:05 on 29 October 1944, I-12 was submerged 1,000 nautical miles (1,900 km; 1,200 mi) northeast of Oahu, Hawaii, when she fired two torpedoes at John A. Johnson, which was making 8.9 knots (16.5 km/h; 10.2 mph) in rough seas.

[6] I-12 merely brushed the lifeboat, but immediately opened fire on its occupants and men in the water who had jumped out of the boat with her 25 mm antiaircraft guns as 10 to 15 members of her crew on deck shouted Banzai!

[15] The airliner's crew and passengers also saw John A. Johnson′s bow section explode at 01:05, sending flames 700 feet (213 m) into the air, after which it sank.

[6] The aircraft reported the sighting to authorities in San Francisco, who in turn notified the United States Navy patrol vessel USS Argus (PY-14), whose crew had heard the explosion of John A. Johnson′s bow section from 90 nautical miles (170 km; 100 mi) away and already was headed toward the scene.

[6] One source claims that four crewmen, five Navy Armed Guard personnel, and the U.S. Army cargo security officer were left missing and presumed dead,[6] and another specifies that 10 men died.

[6] On 13 November 1944, the U.S. Navy minesweeper USS Ardent (AM-340) and the United States Coast Guard-manned U.S. Navy patrol frigate USS Rockford (PF-48) were escorting a six-ship convoy at about the midpoint of its voyage from Honolulu to San Francisco when at 12:32 Ardent′s sonar detected a submerged submarine ahead of the convoy 1,000 nautical miles (1,900 km; 1,200 mi) west-southwest of Los Angeles, California.

Ardent carried out two more Hedgehog attacks and Rockford dropped 13 depth charges to ensure the submarine′s destruction.

However, Japanese signals intelligence intercepted Allied communications indicating the sinking of an Allied transport and tanker in the mid-Pacific Ocean between 20 and 31 December 1944[6] and U.S. Navy sightings of a Japanese submarine in the Hawaiian Islands area on 2 and 4 January 1945, leading the 6th Fleet staff to conclude that I-12 still was on patrol.

[6] The 6th Fleet staff also assessed that a garbled interception of an Allied report of a surfaced Japanese submarine seen north of the Marshall Islands at 14°10′N 171°02′E / 14.167°N 171.033°E / 14.167; 171.033 on 5 January 1945 was a sighting of I-12 as she returned from her patrol.

[6] On 31 January 1945, however, the Imperial Japanese Navy declared I-12 to be presumed lost with all 114 hands in the mid-Pacific Ocean.