American forces could use another tank besides the Renault FT. Its twin Model T Ford engines were controlled by the driver (seated at the front), while the gunner sat beside him and controlled a .30-06 machine gun (either the M1917 Marlin or M1919 Browning) on a limited-traverse mount. A contract for 15,000 of these vehicles was awarded; however, the U.S. Tank Corps felt that the design did not meet their requirements. The contract for the 15,000 tanks was ended after the Armistice, when only fifteen had been produced. Post-World War I After the end of the conflict, the U.S. Army was reorganized. In 1919, Pershing recommended to a joint session of the Senate and House Committee on Military Affairs that the tank be subordinated to the infantry. As a result, the 1920 National Defense Act disbanded the U.S. Tank Corps, and reassigned its tanks to the infantry branch, with only two heavy tank battalions and four light tank battalions escaping post-war demobilization. The M1917 tanks came too late, and did not take part in any combat during the war. Afterwards, however, five accompanied the U.S. Marine Expeditionary Force to Tianjin in April 1927 under General Smedley Butler. They returned to the U.S. in late 1928. After the Tank Corps was abolished as a separate branch, and control of tanks handed to the infantry, the number of tank units was progressively reduced, and the vehicles mothballed or scrapped. The Tank Mark VIII (or "Liberty", after its engine) was an Anglo-American tank design of the First World War, a collaborative effort to equip France, the U.K., and the U.S. with a single heavy tank design built in France for an offensive in 1919. Testing of the design was not finished until after the war, and it was decided to build 100 vehicles in the U.S.; these were constructed in 1919 and 1920. The American Liberty tanks equipped a single unit: the 67th Infantry (Tank) Regiment, based in Aberdeen, Maryland. The curious designation of the unit had its origin in the fact that since 1922 by law all tanks had to be part of the Infantry. Some Liberty tanks were assigned to the 301st Tank Battalion (Heavy), later redesignated the 17th Tank Battalion (Heavy). Throughout most of 1921 and 1922, Major Dwight D. Eisenhower commanded this unit. Although the tank of World War I was slow, clumsy, difficult to control, and mechanically unreliable,