Using side-firing weapons on aircraft can be traced back to 1927, when a concept was demonstrated by fixing a .30 caliber machine gun to the side of a biplane and flying a simple maneuver known as a pylon turn. Named after the air racing term, it involved positioning an aircraft in a gentle bank and orbiting it around a fixed point as the gun fired continuously. Yet, when Army brass watched the demonstration, which showed promise, they dismissed it as strange and useless, ordering the idea shelved as they moved on to more familiar things. Another effort was made to garner interest in 1939, as just as war clouds loomed, but it too fell by the wayside. Ultimately, it would take an American commander in Queensland, Australia to force the Air Corps to realize the potential of the idea.

In 1943, with the U.S. deep in World War II, Army Air Corps Major Paul “Pappy” Gunn unknowingly laid the seeds of what would become the gunship, when he added four .50 caliber machine guns to the nose of his squadron’s A-20 Havoc light bombers. Using them as strafers, he soon realized that, though additional firepower helped, it remained barely adequate to achieve what he really needed them to do: sink Japanese shipping. Therefore, he sought out a more suitable airframe in B-25D Mitchell medium bombers, and mounted four .50s in the nose, two on either side of the fuselage and three behind the front nose wheel bay. As this arrangement was never part of the original design, all modifications had to be made in the field. Nevertheless, the improvements worked, and Gunn’s A-20s and B-25s soon flew into action in a big way.

From March 2-4, the Battle of the Bismarck Sea raged as aircraft of the U.S. and Australia intercepted a Japanese convoy of eight transports carrying men and material to reinforce Lae, New Guinea.

Gunn’s A-20s and B-25s swept in at low level, hammering the hulls and decks of the transport ships and their naval escorts with bombs and tens of thousands of rounds. The attacks were relentless, and at the end of the battle all eight of the transports slipped beneath the waves, smoldering and peppered from bow to stern with bullet holes. The modifications worked, and the gunships success echoed back to designers who, months later, produced G and H models of the Mitchell sporting armaments up to 75mm.