The Mitsubishi B1M was a Japanese torpedo bomber of the 1920s, also known as the Navy Type 13 Carrier-Borne Attack Aircraft. It was designed and built by Mitsubishi and used in combat against China. The aircraft was used by the air services of the Imperial Japanese Navy and Imperial Japanese Army. Development While working with the Mitsubishi company, the British aircraft designer Herbert Smith designed the 2MT1 two-seat biplane torpedo bomber which flew for the first time in January 1923. It went into Japanese Navy service as the Type 13-1 carrier-borne attack aircraft or B1M1, and was followed by the 2MT2 and 2MT3 variants (also designated B1M1). The redesigned Type 13-2 was designated B1M2. The final version, the Type 13-3 or B1M3, had the company designation 3MT2 and was a three-seater. Total production was 443. The B1M was powered by a Napier Lion or Hispano-Suiza engine according to version. Operational history The type entered service in 1924 and served into the 1930s, 32 flying from the aircraft carriers and during the Shanghai Incident in 1932. An aircraft from Kaga was lost during an aerial engagement between an American air force adviser and demonstration pilot to the Chinese government, Robert Short, who also lost his life, and regarded as a hero defending the Chinese city against the Japanese aircraft. Four days later, a 15-aircraft formation composed of Nakajima A1N fighters and B1Ms attacked Qiaosi Airbase in Hangzhou, and in the ensuing dogfight, at least one Chinese Junkers K 47 fighter was shot down. From 1929, a number of surplus B1Ms were converted for civilian use, being fitted with an enclosed cabin for passengers or cargo. Variants Navy long formal designations Navy Type 13-1 Carrier Attack Aircraft B1M1 Navy Type 13-2 Carrier Attack Aircraft B1M2 Navy Type 13-3 Carrier Attack Aircraft B1M3 Navy short designations B1M1 Initial two seat production version powered by Napier Lion engine. . 197 built by Mitsubishi. B1M2 Three-seat production torpedo bomber, based on 2MT5, powered by Mitsubishi Hi V-12 engine. 115 built by Mitsubishi. B1M3 Improved B1M2 with revised propeller and reduction gear. 128 built by Mitsubishi and Hiro Naval Arsenal. Company designations 2MT1 Navy Type 13-1 Carrier Attack Aircraft / B1M1 2MT2 Navy Type 13-1 Carrier Attack Aircraft / B1M1 2MT3 Navy Type 13-1 Carrier Attack Aircraft / B1M1 2MT4 Ohtori Experimental reconnaissance seaplane version. One built. 2MT5 Tora Prototype of the B1M2 / Navy Type