This Japanese Navy and Air Force engine is the type that powered World War II Allied Code Names George, Sam, Rita, and Frank aircraft. After overcoming some initial reliability problems including vibration and difficult servicing, the Nakajima Homare became the most important 18-cylinder Japanese engine toward the end of the war. Between 1941 and 1945, 8,771 engines of all models of the Homare 10 and 20 series were manufactured.

A very compact design, it had a very high specific output, but had difficulty providing rated power at altitude. For the first time in a Japanese engine, it incorporated a steel crankcase, dynamic balancers, a dual magneto with a remote distributor (on the nose), and a nose sump pump. Its supercharger drive followed the Wright Aeronautical design, with a planetary reduction gear in series with the high gear for obtaining a lower compression ratio, and was equipped with water-methanol injection.