The most formidable torpedo in any nation’s arsenal in World War II was the Japanese Type 93, or Long Lance, as it was called because of its extremely long range. This weapon could carry a half ton warhead for 11 miles at 49 knots, or a fantastic 22 miles at 36 knots. It was principally a cruiser and destroyer launched weapon, but its range and speed were so great American commanders frequently attributed the source of a torpedo attack to an undetected submarine.
The Type 93 was developed by the Japanese in complete secrecy in an attempt to offset the perceived Anglo-American advantage in capital ship tonnage resulting from the 1922 Washington Naval
Treaty. The Japanese were able to achieve the great range and speed of the Type 93 by using pure oxygen as the oxidant, rather than compressed air, as was the case with the standard Whitehead torpedo design then in use in most navies. Other navies had experimented with oxygen, but had given up on it as being inherently too unsafe after a series of disastrous explosions. The Japanese persevered and ultimately mastered the techniques of handling oxygen by meticulous attention to design detail, elimination of all sharp curves in oxygen feed piping, purging to eliminate all oil and grease from the oxygen system, and using compressed air to start the engine before switchover to oxygen.
The Type 93 showed its effectiveness early in the war at the battles of Java Sea, Sunda Strait and Savo Island. At Tassafaronga in November 1942, a Japanese task force under Rear Admiral Tanaka sank the USS Northampton and badly damaged three other cruisers exclusively with Long Lance torpedoes. Among American and allied ships sunk or badly damaged by the Type 93 were the cruisers USS Chicago, Vincennes, Houston, Salt Lake City, Northampton, Boise, Juneau, Portland, New Orleans, Pensacola, Minneapolis, Helena, Honolulu and St. Louis; HMAS Canberra and Perth; HMNS Java and DeRuyter; and HMS Exeter. The smaller submarine version of Long Lance sank or finished off USS Juneau, Wasp, Yorktown and Indianapolis. Despite these successes, as the war continued the Imperial Navy experienced irreplaceable losses of cruisers and destroyers from which to launch the Type 93, and damage to the Americans consequently decreased. In an effort to reverse this misfortune, in 1944, the Japanese began to convert Type 93 torpedoes into miniature submarines by adding a pilot station and a double sized warhead. The mini-sub would be carried by fleet submarines and be launched submerged close to the intended target, thus correcting for the shortcomings of earlier mini-sub models which had to be launched on the surface far from the target. The new weapon was given the name kaiten, which means “sky change”, and presumably was intended to convey a sense of revolutionary change in the direction of Japan’s naval fortunes.
The kaiten was the brain child of a pair of mini-sub pilots, Lieutenant (j .g.) Sekio Nishina and Lieutenant Kiroshi Kuroki. They conceived the idea in 1942 but were repeatedly put off and were not given a go-ahead for another year, and then not until they had submitted their proposal signed with their own blood. Still the Japanese Navy Ministry dithered and didn’t become serious about deployment of kaiten until after the disaster of the battle of Philippine Sea in June 1944.
The first deployment of kaiten was against allied warships in Ulithi Atoll on the night of 19 November 1944. The submarine 1-47 launched four kaitens, led by Nishina carrying with him the ashes of his comrade Kuroki, who had died in a training accident. Nishina penetrated the anchorage and sank the fleet oiler Mississinewa in a blaze which lighted up the whole anchorage. The other kaitens made no hits.
Unfortunately for the Japanese, the promising beginning at Ulithi was the high point of kaiten history. Besides Mississinewa, the only other serious damage to a U.S. ship by a kaiten was to the destroyer Underhill which lost its bow and later had to be sunk. Japanese submarines sortied thirty times on kai ten missions, each carrying four to eight kaitens on deck. Eighty kaitens were launched, but a greater number had to be back-hauled due to malfunction . Eight submarines were lost on kaiten missions and ninety-six pilots gave their lives in combat or training.
The Undersea Warfare Museum at Keyport acquired a kaiten mini-sub last winter and is in the process of restoring it . This interesting combination of torpedo and submarine should be an important reminder that innovative advancement in weapon technology is not the exclusive province of the western world.
Reprinted from the Naval Undersea Warfare Museum Foundation Newsletter, Number 5, by special permission of its editor, Ralph E. Enos.