The Willys MB and the Ford GPW, formally the U.S. Army Truck, -ton, 4×4, Command Reconnaissance, informally the Willys Jeep, Jeep, or jeep, and sometimes referred to by its supply catalogue designation G503, are American off-road four-wheel drive military light utility vehicles, built in large numbers to a single standardized design, for the United States and the Allies of World War II from 1941 until 1945. The U.S. Army had been requesting a small, light four-wheel drive vehicle since the early 1920s, because in World War One both motorcycles and sidecars plainly failed as mechanizations of the ridden horse in all roles. Though early concepts were prototyped in the 1930s, the jeep's actual design and development took place in 1940–1941. As it became the primary light wheeled multi-role vehicle of the United States military and its allies, it became the world's first light four-wheel drive motor vehicle produced in 6-figure numbers. The jeep became the workhorse of the U.S. military during the war, replacing horses and other draft animals (still heavily used in World War I) in almost every role from cavalry to logistics, while improvised field modifications made the jeep capable of performing practically any other function necessary. An amphibious variant of the jeep, the Ford GPA, was also produced, but its flaws compared to other Allied amphibious vehicles led to its quick discontinuation. With almost 650,000 units built, the jeep constituted a quarter of the total U.S. non-combat motor vehicles produced during the war, or almost two-thirds of the 988,000 light 4WD vehicles produced, when counted together with the Dodge WC series. The jeep massively outproduced its primary Axis counterpart, Nazi Germany's Volkswagen Kübelwagen, which only had a production total of 50,000 units. Large numbers of jeeps were provided to U.S. allies through Lend-Lease. The jeep was widely revered for its reliability and wide usage. Supreme Commander of the Allied Expeditionary Force General Dwight D. Eisenhower wrote in his memoirs that most senior officers regarded it as one of the five pieces of equipment most vital to American victory in Africa and Europe. Chief of Staff of the U.S. Army General George C. Marshall called the jeep "America's greatest contribution to modern warfare." Historian Charles K. Hyde wrote: "In many respects, the jeep became the iconic vehicle of World War II, with an almost mythological reputation of toughness, durability, and versatility." In 1991, the Willys MB was designated