.jpg "M931) 5-ton (m818 Tractor Truck")
The 5‑ton 6x6 truck, officially “Truck, 5‑ton, 6x6â€, was a class of heavy-duty trucks used by the US Armed Forces. The basic cargo version was designed to transport a 5-ton (4,500 kg), 14 ft (4.27 m) long load over all terrain in all weather. Through three evolutionary series (M39, M809, and M939) there have been component improvements, but all trucks were mechanically very similar. They were the standard heavy-duty truck of the US military for 40 years, until replaced by the Medium Tactical Vehicle (MTV) beginning in 1991.
A 20 June 1945 report by the Army Ground Forces Equipment Review Board recommended that all 4‑ton to 6‑ton tactical trucks should be replaced by a single standard 5‑ton (4,536 kg) 6x6 truck series. In 1949 specifications were set and truck manufactures began working on prototypes. Chrysler, GMC, and Mack’s designs were advanced, International Harvester’s was a conservative conventional, similar in size and layout to the earlier 6-ton (G512) series.