The Diamond T M20 Truck, 12-ton, 6x4 and 45-ton M9 trailer were developed during World War II as a transporter for the M4 Sherman tank. The combination of truck and trailer together had the nomenclature "Transporter, Tank, 45-ton, M19". The transporter was also used for general cargo such as ammunition and fuel.
The Diamond T M20 was also known as Model 820 and was equipped with a Hercules diesel DFXE engine. The engine compartment was opened from either side, with the covers hinged along the center line of the hood, front to back (sometimes called butterfly wings). The cab was made in both open, soft-top and closed, hard-top variants. A machine gun ring mount could be provided with the soft top, on the passanger side of the cab. In the space between the cargo box and the cab, pioneer tools and fuel can carriers were mounted and a large winch occupied the floor.
Diamond T M20 12 Ton Truck and M9 Trailer loaded with ammunition as part of a Red Ball Express convoy, France, 1944.