 The M274 Mule was introduced in 1956 to supplement both the 1/4 ton trucks ("Jeeps") and 3/4 ton trucks (Weapons Carrier Series and M37 series) in airborne and infantry battalions.The M274 evolved from improvements to a vehicle designed at the end of World War Two by Willys-Overland as a medical evacuation litter carrier from areas and terrain that would even be a problem for its famous Jeep to access.Further tests by the US Army at Eglin Field, Florida proved it also useful as carrier for both supplies and men.