In 1940, the Army wanted all new off-road trucks. They wanted , , , and 5-ton 4x4s. They also wanted , 4, 6, and -ton 6x6s. Trucks were tested and changed. Good trucks were built in large numbers. Some good trucks were built by more than one company. (6-ton trucks were built by 5 companies.) In some sizes, more than one type were built. There were 3 different -ton trucks built. Trucks were named after their builder and model. Sometimes they were named by their size and how many powered wheels they had (-ton 6x6). "M" numbers were used to name the bodies.