The M3 Gun Motor Carriage was a tank destroyer used by Allied forces in WWII. The GMC was a modified M3 Halftrack APC fitted with a 75mm gun. It saw use under the US Army in the Philippines, North Africa and Italy, and was used to some extent by other Allies at the Western front. It was removed from service in 1944.
The driver, aside from operating the vehicle, is able to fire the 75mm gun. The damage caused by this gun is weaker than that of a regular artillery shell, though more effective than a regular medium tank gun. This is made up for by the mobility that the vehicle possesses, being able to accelerate quickly and achieve a relatively high speed, just as the regular M3 Half-track. The second passenger mans an M2 Browning mounted on a rail at the back of the vehicle. Finally, the GMC can carry one additional passenger, who does not have weapons at his disposal and cannot use his equipment.
The combination of mobility and firepower make for a unique tactical style not common among other vehicles. However potent the GMC's main attributes make it appear, it does have several drawbacks which limit its flexibility. Chiefly, the lack of a turret relegates the 75mm to a very narrow frontal arc, making it awkward to use in close combat. Combined with poor on-the-spot vehicle traverse, the GMC is often unable to respond to immediate threats. As a result, it is paramount to vehicle's success that its driver be aware of battle conditions and always seek to control the nature and occurrence of engagements. All three occupants are exposed to some degree; the driver and passenger can be shot at through viewports on the front or through the open roof, while the rear gunner's upper body is fully exposed. Despite being based on an APC platform, the M3 GMC does not retain healing or resupplying abilities.