The M4 18-ton High Speed Tractor was designed as a prime mover for towing large field artillery guns such as the 90mm Anti-Aircraft gun, the 155mm Long Tom, the 8in. Howitzer, or other heavy weapons (See the Towed Artillery Chart). In addition to moving the gun, the M-4 High Speed Tractor carried ammunition in cargo space racks. Ten men plus the driver could be carried. The M-4 HST was manufactured by Allis-Chalmers Mfg. Co. of Milwaukee, WI starting in 1942 and was in U.S. military service until approximately 1960.
The M-4 High Speed Tractor was equipped with air and electric brakes that would match any types of brakes on the towed load.
An anti-aircraft .50 cal. machine gun on a ring mount was accessed through a hatch above the crew compartment.