United States entered the First World War under its curtain in 1917. American troops arrived in France, had heavy weapons in the form of eight-inch howitzers British Mk Mk VII and VIII, which were manufactured in America by the British orders. Having experienced these howitzers in combat, the Americans in the postwar period have decided to adopt a similar artillery systems under the name M1 two calibers: 6.1 inches by 8 inches, which corresponds to the metric system of 155 mm and 203 mm. Both guns were mounted on the same carriages, but smaller caliber gun had a longer barrel and less weight. Compared with the English prototype 8-inch howitzer M1 has been significantly improved: it somewhat lengthened barrel and entered triaxial sprung wheel turn. However, long-distance 203 mm gun transported disassembled into two parts using a fast-tracked tractors M35.
prototypes were tested and adjusted for quite some time, and therefore howitzer entered the U.S. Army in 1940 only. It was used in the battles of the Second World War, as well as the Korean and Vietnam wars. In 1946 upgraded howitzer firing high-explosive grenades new M106 and M115 renamed.
203-mm gun was mounted on a tank chassis also M4AZ Sherman - such self-propelled gun was designated M43. Both towed and self-propelled variants in, M115 howitzer for his time differed good accuracy and range of fire. She was armed with NATO countries for several decades and is currently stored in the arsenals of many armies as a weapon allowance, as can fire nuclear warheads M422.