The United States Army first worked on a 120 mm gun after the end of
World War I, with a prototype being presented in 1924. The system was considered far too heavy and expensive to be useful, and the project slowed, although it was never canceled outright. In 1938, the Army reviewed its needs for newer AA systems and decided to order new systems for both the heavy and super-heavy role. The former was filled by the new
M1 90 mm gun, which replaced the earlier
M3 3-inch gun then in use. For the super-heavy role, the 120 mm gun design was dusted off and mated to a new eight-wheel carriage, designated
4.7-inch M1 when it was accepted in 1940. Like the 90 mm, the M1 gun was typically operated in a battery of four guns, initially with an associated
searchlight,
SCR-268 radar (replaced later by the much-improved
SCR-584),
M10 gun director, and M4
Gun Data Computer that automatically laid the guns. The
M6 tractor was used as the prime mover. The M1 gun entered service late in
World War II. One battalion of M1 guns, the 513th AAA Gun Battalion, was deployed in the Philippines in February 1945, but never fired on any hostile aircraft. After World War II ended and the
Cold War with the
Soviet Union began, M1 guns were deployed in many locations in the U.S. and Canada. To defend against long range Soviet
Tu-4 bomber attack, the
Army Anti-Aircraft Command (ARAACOM) formed 44 active duty and 22
National Guard battalions equipped with M1 guns, divided into seven brigades and 20 anti-aircraft artillery groups. Two Canadian anti-aircraft battalions were also equipped with M1 guns for the joint defense of the
Soo Locks. These guns were guided by the long range
Lashup Radar Network equipped with
AN/CPS-5. M1 guns were deployed for the protection of nuclear production facilities, major industrial centers, strategic air force bases, and select major population centers. In 1954, the
MIM-3 Nike Ajax surface-to-air missile became operational with ARAACOM. It substantially outranged the M1 gun, rendering it obsolete. ARAACOM began retiring the M1 gun from active-duty units and then from National Guard units. Then in 1957, the Soviet Union introduced the
R-7, its first
ICBM, and the M1 gun became practically useless. By January 1960, all remaining National Guard units with M1 guns were converted to Nike missiles or deactivated. ==Modification as a tank gun==