A Kégresse track is an unusual kind of rubber tracks which uses a flexible belt rather than interlocking metal segments. It can be fitted to a conventional car or truck to turn it into a half-track, suitable for use over rough or soft ground. Conventional front wheels and steering are used.
The Kégresse propulsion and suspension system incorporates an articulated bogie, fitted to the rear of the vehicle with a large drive wheel at one end, a large unpowered idler wheel at the other and several small guide wheels in between, over which run a reinforced flexible belt. The belt is fitted with metal or rubber treads to grip the ground. It differs from conventional track systems by using a flexible belt rather than interlocking metal segments.
The name comes from the system's inventor Adolphe Kégresse, who designed the original while working for Tsar Nicholas II of Russia between 1906 and 1916. He applied it to several cars in the Royal garage including Rolls-Royce cars and Packard trucks. The Russian army also fitted the system to a number of their Austin Armoured Cars. After the Russian Revolution Kégresse returned to his native France where the system was used on Citroën cars between 1921 and 1937 for off-road and military vehicles.
In the late 1920s the U.S. Army purchased several Citroën-Kégresse vehicles for evaluation followed by a licence to produce them. This resulted in the Army Ordnance Department building a prototype in 1939. In September 1940 it went into production with the M2 and M3 half-track versions. The United States eventually produced more than 41,000 vehicles in over 70 versions between 1940 and 1944.