The Diamond T Company was already known to make large sized trucks that could transport heavy haulage across cities. Their trucks were also rugged and could operate under difficult conditions.

Somewhere in the late thirties, a committee called British Purchasing Commission, based in New York, USA (her prime role was to help countries under German occupation and arrange materials against cash). In 1940 the Commission after flirting with several automakers decided to give an order for 200 trucks that would carry battle tanks and move heavy artillery guns. That product was a Diamond T Tank Transporter, a 12 ton 6 x 4 truck trailer cab with a 12 wheel trailer model called M9.

Powered by a patented Hercules DFX series engine, it could pull 52 tons of load. By 1941 when the first product rolled out, the Allied Army used them in every battle. By the end of the war, the firm supplied nearly 6000 of these. Several of them that were used by the British army in the Burma (now Myanmar) war theater remained here, after independence in 1947.

The Indian army used these tank transporters until as late as the 1970s.