The Nakajima Ki-27 was the main fighter aircraft used by the Imperial Japanese Army Air Service up until 1940. Its Allied nickname was "Nate", although it was called "Abdul" in the "China Burma India" (CBI) theater by many post-war sources; Allied Intelligence had reserved that name for the nonexistent Mitsubishi Navy Type 97 fighter, expected to be the successor to the carrier-borne Type 96 with retractable landing gear and an enclosed cockpit.