Aichi M6A - Operational History

Operational History

The first production examples of the Seiran were completed in October 1944. Deliveries were slowed by an earthquake near Nagoya on 7 December 1944, and by an American air-raid on 12 March 1945. Construction of the STo submarines was stopped in March 1945, after two submarine aircraft carriers had been completed and a third finished as a fuel tanker. These were supplemented by two smaller Type AM submarines, originally designed as command submarines carrying reconnaissance floatplanes, but capable of carrying two Seirans. Owing to the reduced carrier submarine force, production of the Seiran was halted, with a total of 28 completed (including the prototypes and the M6A1-Ks).

The new submarines and aircraft were assigned to the 1st Submarine Flotilla, comprising the two STo submarines, the I-400 and the flagship I-401, each carrying three Seirans together with two type AMs, the I-13 and I-14. The 1st Submarine Flotilla commenced training with the Seirans in January 1945, the crews gradually learning how to handle the submarines and aircraft. Launching all three Seirans took longer than expected: 30 minutes if floats were fitted, although this could be reduced to 14.5 minutes if the floats were not used.

The first mission of the Seirans was to be a surprise air strike on the Gatun locks of the Panama Canal, to cut the main supply line for US forces in the Pacific. When the force was finally ready to set off on their mission against Panama, however, Japan's increasingly desperate situation lead to a change in plan, with the target for the attack, called Operation Hikari (Splendour) being switched to the American base at Ulithi Atoll where forces, including aircraft carriers, were massing in preparation for attacks on the Japanese Home Islands. The flotilla departed Japan on 23 July 1945 and proceeded towards Ulithi. However, on 16 August, the flagship I-401 received a radio message from headquarters, informing them of Japan's surrender and ordering them to return to Japan. All six Seirans on board the two submarines, having been disguised for the operation as American planes in violation of the laws of war, were catapulted into the sea with their wings and stabilizers folded (for the I-401) or pushed overboard (for the I-400) to prevent capture.