D-4 Caterpillar Bulldozer
During WW II, the D4 was one of the tractor/bulldozers collectively known as "Tractor, Light." The Caterpillar D4 models were Ordnance G-151. Equivalent tractors were produced during WW II by International Harvester Co. (Model TD9, G-99). The Cat D4 was used as a prime mover for light artillery, for general duty as a tractor, or as a bulldozer when equipped with a suitable blade attachment.
The evolution of the D4 included these models:
- D4 4G series 1937-1938, Orchard model
- D4 7J series 1939-1942
- D4 2T series 1943-1945
- D4 5T series 1945-1947
- D4 6U series 1947-1959, 44 inch gauge
- D4 7U series 1947-1959, 60 inch gauge
Over 7,400 of the 5T series were built and over 44,000 7U units were produced. Tractor serial numbers were composed of the series (eg 4G, 6J) followed by a four or five digit serial number. With modifications and additional series, the D4 continued in production and remains in the Caterpillar product line in the mid-2000s.
Caterpillar D4 tractor in use during Alcan Highway construction, 1942.
Caterpillar D4 tractor in use on Attu Island, Aleutians, May 1943.
Caterpillar D4 tractor configured as a bulldozer belonging to U.S. Fifth Army, on raft in Volturno River, Italy, October 1943.
