Today in WW II: 7 Dec 1941 Japanese attack US Navy at Pearl Harbor, Hawaii, sinking or severely damaging 18 ships: 8 battleships, 3 light cruisers, and 3 destroyers .  More 
7 Dec 1941 Japanese declare war on Britain and United States.
7 Dec 1941 In North Africa, the Afrika Korps fell back to El Agheila, halting their retreat and the British Operation Crusader advance there.
7 Dec 1944 US Army units land at Ormoc Bay, Leyte, Philippine Islands cutting off the Japanese ability to reinforce and supply Leyte.
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M3 37mm Antitank Gun

By 1937 analysis of foreign trends in tank development indicated the need for a heavier weapon capable of greater armor penetration. Development of a new antitank gun, however, experienced the same budgetary constraints and prolonged acquisition cycle as tank designs. Therefore, instead of building a new weapon, the Army opted to purchase a proven, foreign antitank gun already in production. It selected the German 37mm gun built by Rheinmetall-Borsig Company and used by the German Army, the Panzer Abwehr Kanone (PAK)-36. The U.S. military attaché in Germany arranged the purchase of several guns. After extensive testing and minor modification, an American-built version was accepted for service with the U.S. Army.

Designated the M3 37mm Antitank Gun with M4 Carriage the new weapon entered production in November 1939. Field deliveries of the M3 to Army units began in early 1940. Towed by its prime mover, the 4x4 quarter-ton truck (jeep), the gun would trail at 50 mph on roads. When traveling cross-country, gullies, shell holes, mud holes, and slopes of 26 degrees were negotiated with ease.

In addition to being towed on its own carriage by light trucks and jeeps, the 37mm antitank cannon was mounted on the WC-55 3/4 ton 4x4 Gun Motor Carriage -- when the 37mm gun is mounted the combined weapons system is known as the M-6 Gun Motor Carriage (GMC).

The M3 was manned by a crew of four who fired a 1.61-pound projectile with an effective range of 500 yards. The M3 37mm Antitank Gun was followed by the M3A1 which differed only in the addition of a rarely-used muzzle brake, attached by threads on the end of the barrel.

At the time of its adoption, the M3 could destroy any tank then being produced in the world. However, by the time the United States entered the war, the M3 was outmatched by the tanks in use in Europe. Japanese tanks were smaller and more vulnerable to the M3 throughout the war. Heavier armor meant that by the time the Army began fielding the 37mm antitank gun, larger caliber weapons were eclipsing it. The M3 37mm Antitank Gun was replaced by the M1 57mm Antitank Gun in the European Theater, starting in Tunisia in 1943.

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Material on this page adapted from Mobility, shock, and firepower: the emergence of the U.S. Army’s armor branch, 1917–1945 by Robert Stewart Cameron, Center of Military History, United States Army, Washington, DC, 2008, and other sources.

M3 37mm antitank gun towed by a jeep, often its prime mover
M3 37mm antitank gun towed by a jeep, often its prime mover.

M3 37mm Antitank gun
Dodge WC4 (or WC13 w/o winch) towing M3 37mm Antitank gun across the Guadalupe River, Ft. Sam Houston, TX (near San Antonio) in 1942. The photo was taken by Lt. Edward Y. Pettit, 2nd Eng., 2ID. He was promoted to Captain and won a Silver Star in Normandy, while Company Commander of Company C, 2nd Combat Engineers Battalion, 2nd (Indianhead) Infantry Division, 14 June 1944. Photo: Courtesy of Bob Pettit, son of Capt. Pettit.

M3 37mm Antitank gun
M3 37mm antitank gun crew training at Fort Benning, GA, April 1942.

M3 37mm Antitank gun
M3 37mm Antitank Gun at at Pate Museum of Transportation. Photo: Courtesy of Bob Pettit.

M3 37mm Antitank gun
M3 37mm Antitank Gun at at Pate Museum of Transportation. Photo: Courtesy of Bob Pettit.

M3 37mm Antitank gun
Data stencil, M3 37mm Antitank Gun at at Pate Museum of Transportation. Photo: Courtesy of Bob Pettit.