In 1940, the Willys Quad was built to compete against the Bantam reconnaissance car for evaluation by the U.S.

[2] The two prototype Quads were powered by the Willys “Go-Devil” engine that turned out to be the automaker's greatest asset.

[2] Willys' pilot vehicle was overweight compared to the Army's requirements, but the "Go Devil" engine rated at 55 hp (41 kW; 56 PS) included a heavier transmission, a combination that proved to be beneficial in the long-run for use in cross-country travel.

[4] Roos took the "less than impressive" 48 hp (36 kW; 49 PS) automobile engine and increased its performance and durability.

[5] The specifications by the Quartermaster Corps called for only 85 lb⋅ft (115 N⋅m) of torque at the rear axle.