The M20 was a derivative of the M8 Greyhound series. The chief difference between the two armored cars was the absence of a turret which allowed the M20 to feature benches and specialized radio equipment for use as an artillery spotter, reconnaissance vehicle, or personnel carrier.
It had a Hercules JXD engine that was capable of propelling it at speeds of up to 90 kilometers per hour. For defensive armament, the vehicle also had a 12.7 mm browning machine gun along with any weapons such as M1 Garands or M1 Bazookas that the infantry on board would have carried. It was recommended that personnel on board the vehicle carried a wide variety of weapons in case the vehicle was separated from its unit. The total weight of the M20 was about 6,800 kg while the total length was the same as the original Greyhound, 5 meters. It was well liked by its crews and proved quite reliable where it was used.
The M20 was initially developed as the M10 reconnaissance vehicle but was redesignated so that it would not be mistaken for the M10 Tank Destroyer. It was developed in 1943 because of the US Army's need for a mobile vehicle that could serve as an anti aircraft role if necessary and haul cargo. In total, around 3,680 M20s were built by the end of the war.