The Diamond T Company had a long history of building rugged, military vehicles for the U.S. Army Quartermaster Corps and had recently produced a prototype heavy vehicle for the US Army which, with a few slight modifications met British requirements and an initial order for 200 was very quickly filled.

Powered by a Hercules DFXE diesel engine developing 201 hp (150 kW) and geared very low, it could pull a trailer of up to 115,000 lb (52 t) and proved capable of the task of moving the heaviest tanks then in service.

[5][6] A two plate dry disk diaphragm spring clutch drove Fuller four-speed main and three-speed auxiliary transmissions.

This used four brake pads with a cable clasp mechanism onto a 16 in (41 cm) disk, mounted behind the auxiliary transmission.

The box could hold 18,000 lb (8,200 kg) of ballast to increase traction on the rear tandem axles.

Cable rollers and sheaves let the winch from the M20 truck pull tanks onto the trailer, chocks and chains were used to secure the load.

[2] The first batch was received in Britain in 1942 and very quickly demonstrated their rugged reliability in the British campaign in North Africa.

U.S. forces in Europe preferred the M25 tank transporter, citing the fact that the M19 suffered from a wide turning radius, poor traction of the truck, and excessive rolling resistance.

Five 1 short ton (910 kg) concrete blocks were routinely carried in the bed of the truck to improve traction; the conversion of an M20 truck and M9 trailer to a semi-trailer configuration rather than a trailed configuration alleviated some of these problems, and also improved fuel economy by approximately fifty percent.

[citation needed] Many of the 70-year-old Diamond Ts can still be found in private ownership in Britain and frequently appear at historic vehicle shows.

[citation needed] This combination unit is referred to as the M19 tank transporter, consisting of the M20 tractor and M9 24-wheel trailer.

In the nomenclature system used by the United States Army Ordnance Corps Supply Catalog this vehicle is referred as the G159.