During World War II, the Mitsubishi Army Type 1, Ha 31 Model 21 (Ha 102) powered the Mitsubishi Ki-46-II/II KAI, Army Type 100 command reconnaissance aircraft (Allied Code Name DINAH 2), Kawasaki Ki-45 KAI/b/c/d Army Type 2 two-seat fighter Toryu (Allied Code Name NICK), and MC-20 II transport (Allied Code Name TOPSY). There were 7,852 Ha 102 engines built between 1938 and 1945.

The engine type is a highly developed version of the Japanese Navy Zuisei Model 10 series designed in the mid-1930s. The original Model 11 was rated at 649 kW (870 hp) at 2,540 rpm. Following adoption of the “Unified Type Designation System,” the Army’s version of this model was known as the Ha 31-21. The Model 21 was a major redesign of the Model 15 that included a new reduction gear and two-speed supercharger.