In 1939, the idea of a universal military vehicle was taking shape as the army sought a replacement for motorcycles with side cars from World War I and vehicles such as the modified Ford Model T. The military set new standards and submitted them to American auto makers, calling for a vehicle with a load capacity of 600 pounds, a wheelbase under 75 inches, a height under 36 inches, an engine that could run smoothly from 3 to 50 miles per hour, a rectangular body, a two speed transfer case with four wheel drive, a folding windshield, three bucket seats, blackout and driving lights, and a gross vehicle weight under 1200 pounds. Although 137 companies were invited to submit designs, only three did. Willys-Overland received the production contract and began production in 1941. More than 350,000 Jeeps were produced during the 1940s in support of the war effort, at a military cost of $738.74 per vehicle, and Ford also built the vehicle during the war using Willys-Overland blueprints. The name Jeep is generally accepted to have come from Ford's term GP, for general purpose, which when slurred together sounded like Jeep, and Willys made Jeep its trademark. After the Second World War, Willys recognized a large market among returned servicemen for a civilian version and had begun promoting the Jeep's versatility as a work and recreational vehicle as early as 1942, though all production had been allocated to the military. Jeeps have been used since World War II and continue in service with all military branches, and this particular vehicle served in the Korean War.