90 mm gun M1/M2/M3

The 90 mm gun M1/M2/M3 was an American heavy anti-aircraft and anti-tank gun, playing a role similar to the German 8.8cm Flak 18. It had a diameter bore, and a 50 caliber barrel, giving it a length of . It was capable of firing a shell horizontally, or a maximum altitude of . The 90 mm gun was the US Army's primary heavy anti-aircraft gun from just prior to the opening of World War II into 1946, complemented by small numbers of the much larger 120 mm M1 gun. Both were widely deployed in the United States postwar as the Cold War presented a perceived threat from Soviet bombers. The anti-aircraft guns were phased out in the middle 1950s as their role was taken over by surface-to-air missiles such as the MIM-3 Nike Ajax. As a tank gun it was the main weapon of the M36 tank destroyer and M26 Pershing tank, as well as a number of post-war tanks like the M56 Scorpion. It was also briefly deployed from 1943–1946 as a coast defense weapon with the United States Army Coast Artillery Corps. Each gun cost roughly $50,000 to make in 1940 and utilized up to 30 separate contractors to manufacture. Prior to World War II, the primary US anti-aircraft guns were the 3-inch M1918 gun (76.2 mm L/40) and 3-inch anti-aircraft gun M3 (76.2 mm L/50), a widely used caliber for this class of weapon. Similar weapons were in British, Soviet and other arsenals. There had been several upgrades to the weapon over its history, including the experimental T8 and T9 versions developed in the early 1930s, that were intended to enter service later in that decade. However, the US Army became interested in a much more capable weapon instead, and on June 9, 1938, it issued a development contract calling for two new guns, one of 90 mm, which it felt was the largest possible size that was still capable of being manually loaded at high elevations, and another, using assisted loading, of . On 18 August 1938 the development of the Mounting T1 was approved as well. The new design seemed so much better than developments of the older three-inch that work on the three-inch T9 was canceled in 1938, just as it became production-ready.