T9E1 75mm Cannon During World War II, the AAF equipped its B-25G and B-25H medium bombers and some Douglas A-26B light bombers with a single-shot manually loaded 75mm cannon in the nose. Though only three of four rounds could be fired during a single attack run on a target, these aircraft caused considerable damage to enemy shipping and ground targets, particularly in the Pacific. Although automatic feed mechanisms were designed to increase the rate of fire, the successful employment of aircraft rockets late in WWII halted further development of heavy aircraft cannon. But in the 1960s, the development of heavy rapid-fire cannon was resurrected for use in Southeast Asia and in other advanced ground attack applications. Click here to return to the Cold War Gallery.