 A total of 2,064 aircraft were built, 1,713 by Mitsubishi and 351 by Nakajima.The Ki-21-Ia was used in combat in the war with China by the 60th "Sentai" from autumn 1938, carrying out long-range unescorted bombing missions in conjunction with the BR.20 equipped 12th and 98th "Sentai"s. The Ki-21 proved to be more successful than the BR.20, having a longer range and being more robust and reliable.Two more "Sentai"s, the 58th and 61st deployed to Manchuria in the summer of 1939 for operations against China, with aircraft from the 61st also being heavily used against Russian and Mongolian Forces during the Nomonhan Incident in June–July 1939.