The advent of aircraft as effective tools of war in World War 1 prompted the need for ground-based artillery to track and ultimately engage and destroy such airborne enemy targets. The United States Army began work on such a weapon but the end of the war signaled a massive slowdown in the requirement and the program proceeded at a snail's pace until a new world war seemed all but inevitable with Hitler, Mussolini and Stalin moving on Europe and North Africa and the Japanese conquests of territories in the Pacific. The US Army dove back into the search for a modern anti-aircraft solution in 1938 and the result became the "4.7-inch M1' - a cannon of 120mm caliber specifically designed to help defeat the new-found threats posed by the Axis air powers - namely metal-skinned monoplane aircraft types that were designed with much improved high altitude capabilities and greater defensive maneuverability than the outmoded wooden biplane aircraft designs seen in the previous world war.The 120mm Gun M1, or "120mm" as most called her (also the "Stratosphere Gun" as nicknamed by others), was the largest anti-aircraft gun constructed in the United States for the US Army during World War 2. She was first deployed in 1940 before the official American involvement in the conflict. Anti-aircraft guns were utilized to deter enemy aircraft from entering airspace by sending up heavy exploding shells at predetermined altitudes. Such defensive measures were fielded by all major powers participating in World War 2 and proved just as deadly a factor to airmen as enemy fighters would. The Germans found double success with their 88mm "FlaK" guns in the anti-tank role as well to which the "88s" fared quite favorably against enemy tank armor.The M1 was conventionally mounted on a towing carriage making use of eight large road wheels set in pairs at each corner of the chassis. These were required to support her massive 62,000lbs (31 ton) transport weight. The M1 gun barrel could be set to fire ve