Mitsubishi Ki-21

The Mitsubishi Ki‑21, known to the Allies as “Sally,” was a twin‑engine medium bomber that served the Imperial Japanese Army Air Service from the late 1930s through World War II. First flown in 1938, the aircraft emerged from Mitsubishi’s earlier G3M design and incorporated a more powerful all‑metal airframe, a fully enclosed cockpit, and retractable main landing gear. Powered by two Nakajima Ha‑5 radial engines delivering around 1,000 hp each, the Ki‑21 could carry up to 750 kg of bombs over a range of roughly 2,400 km at a top speed of 440 km/h. Early models (Ki‑21‑I) suffered from inadequate defensive armament, prompting the introduction of the Ki‑21‑II and later Ki‑21‑IIb variants, which added additional fuselage and wing gun positions and improved armor. The bomber saw extensive action in the China‑Japan War, the early Pacific campaigns, and later as a transport and training platform after frontline service ended. Its reliability and long‑range capability made it a workhorse for Japanese strategic bombing, influencing subsequent designs such as the Ki‑100 fighter conversion. The Ki‑21 remains a symbol of Japan’s pre‑war industrial capacity and the evolution of medium‑bomber doctrine.

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