In 1939-1941 the Army Ordnance Corps was developing a complete line of tactical trucks that could operate over all roads and cross-country terrain in all weather.

[3] The chassis was also the base for Ordnance's standard medium wrecker truck, and was used by the Corps of Engineers for cargo, dump, and specialty bodies.

A crane for chemical weapons and an extra long cargo version for Canada were also built.

In addition to trucks built for Canada, 2,245 were exported under the Lend-Lease Act, most to the British, French, and Canadians.

A transfer case had a high and low range, a neutral for power take-off operation, and engaged the front axle.

[17][18] The basic cargo model was a prime mover used to tow the 155 mm howitzer M1 and transport the gun crew, equipment, and ammunition.

[19][20][21] The wrecker had a Holmes twin-boom design with a swinging boom and powered hoist cable on each side.

The body had low sides on the rear half which tapered to the floor in the front, making clearance for the boom to swing.

Welding tanks, an air compressor, cables, block and tackle, chains, tow-bars, and other equipment were carried.

[22][23] The prime mover had limited cargo room, and the Engineers wanted a model with a larger body to carry bridge pontoons.

A power take-off on the transfer case, used with the transmission in gear, drove the hydraulic pump, the controls were inside the cab.

When the tailgate was hinged at the top the bottom could be opened while dumping with a lever on the left front corner of the body, just behind the driver's window.

A flatbed with a cab protector and mid-ship mounted winch was used for self-loading and carrying large equipment.