Japanese cruiser Ibuki (1943)

The nihongo|"Ibuki"|伊吹 was the last named heavy cruiser begun by the Imperial Japanese Navy. She was ordered under the 1941 Program as a slightly modified version of the "Tone" class, with eight 200 mm guns mounted forwards, and a flight deck with catapults for several reconnaissance floatplanes at the aft.

Before she was laid down in early 1942 the design was altered to an improved "Mogami" design.

"Ibuki" was to have a similar armament to "Mogami", with ten 200 mm guns mounted in five twin turrets, three turrets at the bow and two at the aft. She was to have a secondary armament of eight 127 mm dual-purpose guns, sixteen 600 mm torpedo tubes and two catapults for three floatplanes. She was to have a maximum speed of 33 knots. The "Mogamis" had been built to save as much weight as possible but had to be extensively rebuilt shortly after trials to fix several defects. Because "Ibuki" was ordered after Japan had withdrawn from the Washington Naval Treaty and was not hindered by the 10,000-ton displacement limitation for cruisers, she was designed to weigh 12,200 tons and make a good balance of armament, armour, speed and seaworthiness.

"Ibuki's" construction was slowed after the Battle of Midway to give priority to aircraft carrier construction. Construction of a second "Ibuki"-class cruiser, designated "No. 301" but never given a name, was begun on the 1 June 1942, but suspended a month later. "No. 301" was scrapped in 1943 but "Ibuki" was launched at Kure Dockyard on the 21 May 1943. Construction was suspended a month later before "Ibuki's" main armament was installed.

Conversion to Aircraft Carrier

The Japanese Navy considered completing "Ibuki" as a fleet oiler for underway replenishment, a capability that the Navy needed. However, since "Ibuki's" hull was already complete and Japan was desperate for carriers, she was towed to Sasebo in November 1943 to be converted to a light aircraft carrier.

"Ibuki" was built with a full-length flight deck and a small starboard island structure. She was to have a very light armament of only four 76 mm and forty-eight 25 mm anti-aircraft guns. Even so, she would only have been able to operate 27 aircraft, less than other Japanese light carriers. In addition, "Ibuki" was to have stern rails for up to 30 depth charges. Her maximum speed was reduced to 29 knots, which was still enough for fleet operations. A radar set was to be fitted and launchers for 120 mm anti-aircraft rockets were later included.

By late 1944 the Japanese Navy was so short of advanced aircraft, trained aircrew and aviation fuel that the shortage of carriers had become irrelevant. However, work continued until March 1945, when shipyard damage and material shortage from American bombing and submarine attacks made construction impossible. When "Ibuki" was surrendered to occupying forces in September, she was 80% complete. She was scrapped at Sasebo in 1947.

"Ibuki" compares favourably in many respects to her American counterparts, both as a cruiser and as a carrier: as a heavy cruiser she was as well armed and armoured as the Baltimore class cruisers, but she was slightly smaller, was fast and as seaworthy. The Independence class carriers, which were converted from incomplete Cleveland class cruisers, were slightly smaller than "Ibuki" but could operate 45 aircraft and were slightly faster. However, the American light carriers were extremely cramped with few aircraft maintenance facilities and were very vulnerable to damage. Because of Japan's long experience with carriers, "Ibuki" probably would also have compared favourably with the German cruiser Seydlitz, which was also scheduled for conversion to a carrier but never finished.