At a. Uttrick peered through his binoculars from the deck of the minesweeper U. Hours before swarms of enemy aircraft descended out of the blue in a sneak attack upon the United States naval base on Oahu, five Japanese midget submarines were already lurking beneath the ocean surface to join in the assault on Pearl Harbor. The Japanese navy considered the foot-long miniature submarines to be their secret weapon. Carrying two men and two torpedoes that had double the explosive charge of those borne by Japanese bombers, the battery-powered midget submarines could glide at 19 knots and operate in the waters of Pearl Harbor that were too shallow for conventional submarines. Flight commander Mitsuo Fuchida, who led the air assault, believed the mini-submarines to be an unnecessary risk that could only endanger the secrecy of the entire operation if they were spotted by the Americans before the bombers arrived.
Transported on board large I type submarines, the midgets were launched near the entrance to Pearl Harbor the night before the attack was to begin. One, spotted trying to enter the harbor before dawn, was attacked and sunk by USS Ward DD in the first combat action of the as yet unopened Pacific War. Another, the Ha , unsuccessful in its attempts to penetrate Pearl Harbor, drifted around to the east coast of Oahu and was captured there the day after the attack. Four of the five Pearl Harbor midget submarines have been found. That sunk by Ward was located by the Hawai'i Undersea Research Laboratory in late August in deep water, some five miles off the entrance to Pearl Harbor.
Contributor: David Stubblebine. By definition, a midget submarine is less than tons, has a crew of no more than eight, has no on-board living accommodation, and operates in conjunction with a mother ship to provide the living accommodations and other support. The Japanese Navy built at least midgets in 7 classes, but only a fraction had any noticeable impact on the war. Their intended purpose initially was to be deployed in front of enemy fleets, but their actual use would be in harbor attacks and coastal defense. The Japanese kept no comprehensive shipbuilding records for their midget submarines.
As part of the attack on Pearl Harbor on December 7, , the Imperial Japanese Navy sent an attack group of submarines to surround Oahu and sink ships attempting to flee. Five of the submarines carried top-secret "mini submarines. They were to surface and fire their torpedoes during the aerial attack. Then, they would dive and escape the harbor, and rendezvous with their "mother submarines," again under cover of darkness the night of December 7.