In the late 1930s the US Army began setting requirements for custom built tactical trucks, winning designs would be built in quantity. As demand increased during WWII some standardized designs were built by other manufactures. Most trucks had gasoline (G) engines until the early 1960s, when multifuel (M) and diesel (D) engines were introduced. Since then diesel fuel has increasingly been used, the last gasoline engine vehicles were built in 1985.