Japanese Torpedo Cruisers
By Mike Bennighof, Ph.D.
September 2018

Exhausted by the First World War, most industrial nations stopped building new warships in its aftermath. Only the United States and Japan truly continued the arms race, with new programs of battleships and light cruisers at the heart of their programs.

Both nations intended their cruisers to perform dual roles: to scout ahead of the battle fleet, and to support destroyer flotillas in action. The American Omaha class and Japanese “5,500-ton type” sacrificed protection for speed and firepower. Japan built 14 of the cruisers in three groups; three more were cancelled when the Washington Naval Treaties were signed in 1922.

As built, the cruisers of the Kuma, Nagara and Sendai classes carried seven 5.5-inch guns, a pair of 3.1-inch anti-aircraft guns and eight torpedo tubes. The first group of five cruisers carried 21-inch torpedoes; the two follow-on classes upgraded to 24-inch tubes. They had great speed at 36 knots, and all of them had mixed oil- and coal-burning power plants.

Sendai-class light cruiser Jintsu, when new.

The Imperial Navy introduced a powerful new torpedo in 1934, the Type 93 oxygen-fueled model. It carried an enormous warhead and had a great theoretical range. In practice, this long range would not prove a great tactical advantage because the torpedo was not a guided weapon and could not be aimed any better than its short-ranged counterparts. But the Japanese had high hopes for it as an equalizer against the larger American battle line. The Naval General Staff planned to open a night action against the Americans by launching hundreds of Type 93 torpedoes in a single salvo; this would hopefully help make up for poor accuracy at very long ranges. The reduced American force would then be engaged at dawn by the untouched Japanese battle line to produce a decisive victory.

A great part of this killing blow would be delivered by a squadron of torpedo cruisers, ships converted to carry dozens of tubes. But not all Japanese flag officers signed on to the tactic, and bureaucratic infighting developed over the concept. Not until 1941 did the torpedo faction win approval for the conversions, and then only for four of the oldest light cruisers in the Navy inventory, a number soon reduced to two. As part of the same program, the Akizuki-class anti-aircraft cruisers then starting construction would be completed as large destroyers, with a bank of four torpedo tubes added amidships.

On 25 August 1941, the light cruiser Kitakami went to Sasebo Navy Yard for conversion to a torpedo cruiser, while her sister Oi went to Maizuru Navy Yard for the same work. Each ship landed three of her 5.5-inch guns and their 21-inch torpedo tubes, and large sponsons were constructed on either side of the ship. Ten banks each with four 24-inch torpedo tubes were placed on the sponsons, giving each ship a total of 40 tubes. Some sources claim they were designed for 44 tubes, but this appears to be inaccurate.

Both ships re-entered service in November, and early the next month sailed with the Combined Fleet’s batteship force as part of their screen. In January, Rear Admiral Matome Ugaki filed a report criticizing the conversions, stating that the ships had been rebuilt without a sound doctrine for their use having been determined. Ugaki’s words apparently resonated with the Combined Fleet command, and the torpedo cruisers dropped out of planners’ thoughts. For the Midway operation, they again sailed with the fleet’s oldest battleships.

Soon after their return from the Midway operation, the two cruisers were earmarked for conversion to fast transports. Ugaki had pointed out that the cruisers did not have the fire control for such a huge number of tubes and would be reduced to firing massive salvoes at vague groupings of enemy ships. If fired at long range as the 1934 tactics advised, most of these extremely expensive weapons would be expended for no result. The admiral had served as Oi’s gunnery officer and appears to have felt that his old ship had been denied her place in Japan’s front-line forces in pursuit of an ill-conceived experiment.

After their second rebuilding, each cruiser now carried two Daihatsu landing craft and 32 torpedo tubes (some sources state 24). They also received a serious upgrade of their light anti-aircraft armament. Through the rest of 1942 and all of 1943, they transported troops to Japan’s far-flung outposts in the Solomons, New Guinea and the Andaman Islands. In January 1944 a British submarine hit Kitakami in the stern with two torpedoes. She barely made Singapore and remained there under repair until June.

Returned to service, Kitakami escorted a tanker to the Philippines but began to take on water from her repaired sections. Drydocked at Cavite, she underwent more repairs but the workers could not fix all of her leaks. She returned to Sasebo Navy Yard in August and remained there in drydock until January 1945. Shipyard engineers recommended removing all but two of her boilers because of the damage, considering it uneconomical to return her to high speed. She was therefore rebuilt as a carrier for eight Kaiten suicide mini-submarines. Armament now became four five-inch dual-purpose guns, 67 25mm anti-aircraft guns, depth charges, and new air- and surface-serach radars, plus a 30-ton crane removed from the seaplane carrier Chitose. She could now make 23 knots.

Fuel shortages limited Kitakami to brief training missions, and she was lightly damaged in July, 1945 by American carrier aircraft attacking the Kure Navy Yard. She was surrendered to the Americans in September and used as a repair ship for vessels used to return Japanese troops to the home islands. In 1946 she was towed to Nanao and scrapped.

Oi, meanwhile, continued transport service for some weeks after her sister’s damage but in March 1944 finally received orders that would lead her into action. She would join four other cruisers and three destroyers on Operation SA-1, a raid into the Indian Ocean against enemy merchant shipping. The Japanese had just one success, when the heavy cruiser Tone sank the freighter Behar on 9 March. The Japanese massacred her crew.

For the next several weeks Oi moved troops and ammunition back and forth in the East Indies. On 19 July the American submarine Flasher hit her with two torpedoes, only one of which exploded. A second spread missed entirely, but Oi had been fatally damaged and sank slowly by the stern.

The two cruisers have fascinated players of naval wargames for decades, but as weapons systems they have to be counted as failures. Ugaki had it right. The huge Type 93 torpedoes were far too expensive to waste in massed fire, and the old, lightly-built cruisers could not have hoped to survive in combat long enough to fire all 40 in careful spreads of four each.

The two ships appear as torpedo cruisers in our Midway Deluxe Edition game. In game terms they are imposing warships with a dozen torpedo factors. The games account for Ugaki’s critique without the need for special rules: Ships are not allowed to “split” their torpedo factors to attack more than one target, meaning that all 12 factors must be assigned to a single American ship, a definite case of overkill. The ships of 1942 are not those of the modern era; they don't have the data management capability to engage multiple targets. Seeing this overkill coming, the American player will take special pains to sink the cruisers before they can get close enough to a high-value target for a torpedo run.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.