The was an anti-aircraft gun developed by the Imperial Japanese Army, which went into production in 1943. The Type 4 number was designated for the year the gun was accepted, 2604 in the Japanese imperial year calendar, or 1944 in the Gregorian calendar. Due to the lack of raw materials available and the great damage by air raids to its industrial infrastructure, only 70 units were made. These units were retained for defense of the Japanese home islands during World War II.