Before American entry into World War II, American manufacturing had already shifted to producing a tremendous amount of equipment, vehicles, aircraft, ships, and ordnance to support the Allied forces. The Second World War was the first mechanized war, one where more soldiers were equipped with or supported by cars, trucks, and tanks than ever before. While American automobile manufacturers had shifted a portion of their production capacity to armored vehicles and trucks, the American production of tanks was at first nonexistent. The National Defense Act of 1920, which restricted tanks to infantry support use only, and a limited army budget led to the lack of American tank manufacture in the interwar years. However, this allowed the American military to develop and test new tank components while observing foreign tanks’ manufacturing and battlefield performance.