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The M-3 Gun Motor Carriage served the U.S. Army’s tank destroyer force temporarily but well.

With war looming in Europe in the late 1930s, the United States began the long, slow process of rearming its military, hoping to achieve field readiness for any prolonged conflict with the European powers. By May 1940, the U.S. Army realized that besides improving its armament it would also need to update its fighting doctrine. Belgium, the Netherlands and France had become the latest European powers to fall to the stunning Nazi blitzkrieg, and it was now apparent that the German army’s highly mobile, tank-heavy mechanized tactics had unveiled a new era of warfare.

U.S. Army planners turned their attention to developing a weapon to counteract the Wehrmacht’s revolutionary tactical fighting approach. They decided that the best way to confront an enemy armored breakthrough was to withhold from the front line a group of mobile antitank guns that could be rushed in quickly wherever needed. These guns would be mounted on self-propelled platforms such as trucks or half-tracks. The call for an interim tank destroyer (TD) design that could be used for training, and perhaps in battle until more sophisticated designs could be produced, went out in July 1941. An order for a test version, designated the T-12, was placed a month later, and 36 T-12s endured successful trials. On October 31, 1941, the design was officially adopted as the 75mm Gun Motor Carriage, M-3.

The M-3, which carried 59 rounds of ammunition, was slightly less than 201⁄2 feet long, with a combat weight of 10 tons and a maximum armor thickness of 0.625 inches. It could travel up to 45 mph and had a range of 200 miles. Its 75mm cannon could penetrate up to 3 inches of armor at 1,000 yards.

As the possibility of war increased for the United States, the Army shipped both the T-12 test models and the completed M-3s to the Philippines, where they arrived in early December, days before the Japanese attack on Pearl Harbor. A provisional field artillery brigade was formed and went into combat when the Japanese invaded the Philippines in January 1942. The dire circumstances facing the American and Filipino troops on the Bataan Peninsula—and the relative paucity of Japanese tanks—meant the brigade served in both regular artillery and antitank roles. When the Philippines fell that May, several M-3s were captured intact. The Japanese used them in a defensive role when Allied forces returned in late 1944.

Stateside in 1942, newly formed Army TD battalions began training on the M-3, and went into action in Tunisia in November. The first American engagement there involved B Company, 701st Tank Destroyer Battalion, which captured the town of Gafsa on November 23 without artillery or infantry support and without suffering a casualty. Later that day, the company ambushed a German armored column near El Guettar, knocking out four tanks in the process, and on the 24th the 701st bagged 14 panzers while capturing the town of Sbeitla. The TD unit took 400 prisoners during the offensive.

On February 20, 1943, German Field Marshal Erwin Rommel routed the Americans at Kasserine Pass, damaging several TD battalions in the process, but the Allies rebounded a month later at El Guettar. The 601st Tank Destroyer Battalion helped throw back an attack by the 10th Panzer Division, firing some 3,000 75mm rounds and knocking out 37 tanks. But it paid a heavy price. With 24 of its 36 M-3s destroyed, the battalion was no longer combat-effective.

As Allied forces turned their attention to Europe, a number of high-ranking American generals expressed a desire either to eliminate the TD battalions or radically scale back their use. There was widespread dissatisfaction among them that the tank destroyers were being used too offensively—as substitute tanks, artillery or assault guns—rather than in their intended defensive role. All the same, it proved difficult for those in the field to resist using the mobile punch the M-3 offered.

When the newer, more capable M-10 replaced the M-3 in the TD battalions, it also was used in an offensive role. Most M-3s were converted to troop carriers, but some continued in a TD role until the end of the war in Italy. British armored units, in fact, used them as self-propelled artillery, issuing them to the headquarters troops of armored car and tank squadrons.

In the Pacific theater, the M-3 saw frontline service throughout the war, mainly as mobile artillery, though it was at a disadvantage in close terrain such as jungles because its open top made it vulnerable to thrown grenades and other explosives. On Saipan in June 1944, Marine TD units had a rare chance to use M-3s in their originally intended role when the Japanese 9th Tank Regiment, supported by infantry, attacked an American beachhead at 3:45 a.m. Having spotted enemy armor the previous day, the Marines were ready and responded with full force. By 7 a.m., only 12 of the 44 Japanese tanks were able to struggle away from a field strewn with wreckage.

For all the intrinsic drawbacks to its hybrid configuration, the M-3 Gun Motor Carriage performed its duties well. It deserves to be remembered as an excellent example of the U.S. Army’s ingenuity in filling an immediate need using on-hand components.


Originally published in the April 2007 issue of World War II Magazine. To subscribe, click here