The design, which used many commercial components to improve reliability and the rate of production, was standardized in 1940 and built by the Autocar Company, Diamond T Motor Company, and the White Motor Company. The vehicle was powered by a 148 hp (110 kW) White 160AX, 386 in 3 (6,330 cc), 6-cylinder gasoline engine. With a fuel capacity of 60 US gallons (230 L), the M3 could carry its crew (one driver) and a squad of 12 soldiers 220 miles (350 km) before refueling, while protecting them from small arms with light armor (6–12 mm of armor ). The suspension consists of a leaf spring for the two front wheels, while the rear treads had vertical volute springs. In the Cold War era, the vehicle was used by a variety of state and non-state operators in conflicts in South America, the Middle East, Africa, and Asia, remaining in service until as late as the mid-1990s.
Although initially unpopular due to its lack of significant armor or a roof to protect the crew from shrapnel, it was used by most of the Allies during the war. They were adapted for a wide variety of uses, such as a self-propelled anti-aircraft weapon or self-propelled artillery. The M3 and its variants were produced by many manufacturers including Diamond T, White Motor Company, and Autocar. Army and Marines, as well as British Commonwealth and Soviet Red Army forces, serving on all major fronts throughout the war. During World War II, the M3 and its variants were supplied to the U.S. The M3 was extensively modified with several dozen variant designs produced for different purposes. Derived from the M2 half-track car, the M3 was extensively produced, with about 15,000 standard M3s and more than 38,000 variant units manufactured. The M3 half-track was an American armored personnel carrier half-track widely used by the Allies during World War II and in the Cold War.