The M4 High-Speed Tractor for World War II was an artillery tractor used by the US Army from 1943.
M4 high speed tractor with 90-mm ammo box
155mm Long Tom howitzer towed behind an M4 High Speed Tractor.
An M4 at Batey ha-Osef Museum, Tel Aviv, 2005
M4 High Speed Tractor at the National Museum of Military Vehicles
An artillery tractor, also referred to as a gun tractor, is a specialized heavy-duty form of tractor unit used to tow artillery pieces of varying weights and calibres. It may be wheeled, tracked, or half-tracked.
Wheeled British WWII Scammell Pioneer towing an 8-inch howitzer
Tracked Finnish WWII Komsomolets (captured from USSR)
Half-tracked German Sd.Kfz. 7 towing an 8.8cm Flak
German RSO artillery tractor towing 105 mm howitzer, Albania, 1943