They were most famously used by the British, French and American armies in World War I for hauling heavy artillery: including BL 9.2 inch Howitzer and the BL 8 inch Howitzer. By 1916 more than 1000 were in use by British and by the end of the war around 10,000 had been used.
There were at least two models used for military purposes: the Holt 75 and the Holt 120. The 120 horsepower (89 kW) model had a tiller-type steering wheel at the front that was usually covered. It weighed about 18,000 pounds (8,200 kg). The 75 h.p. model used two tracks for steering. It had a maximum speed of 15 miles per hour (24 km/h) and had a gasoline engine.
- Holt Tractors Photo Archive: An Album of Steam and Early Gas Tractors, ISBN 978-1-882256-10-5
- "Caterpillar Inc: Roots in Late 19th-Century Endeavors of Best and Holt". International Directory of Company Histories 63. Farmington Hills, Michigan: St. James Press. 2004. ISBN 1-55862-508-9.
- "British 'Tanks' of American Type; Officer of Holt Manufacturing Co. Says England Bought 1,000 Tractors Here". The New York Times. 1916-09-16. p. 1.
- "Vehicles of the A.E.F. During WWI".
Media related to Holt tractors at Wikimedia Commons