In the United States the division of responsibility between the "users" and the design and development side was more clearly defined. After World War I, tanks became an infantry responsibility in the US Army, but in the thirties the US Cavalry was also equipped with tanks in the guise of "combat cars" (for details of circumstances, see Combat Car Ml entry). In July 1940 tank units were taken away from these two "user" arms and organised into the Armored Force, while a Tank Destroyer Command was formed to operate self-propelled guns. In March 1942, the US War Department was reorganised and all "using arms", including the Armored Force and Tank Destroyer Command, became part of Army Ground Forces (AGF). At the same time the various departments which dealt with supply and procurement throughout the army were merged to become the Services of Supply, later called the Army Service Forces (ASF). Virtually unchanged by the reorganisation was the Ordnance Department, although it lost its power to influence the General Staff directly on procurement matters, and became instead dependent on the ASF for procurement authority. The Ordnance Department was responsible for all design and development of US Army ordnance items and, as its name implies, dated from the days when artillery was the main weapon. Tanks, of course, were included among the Ordnance Department's design responsibilities. There was a two-way transfer of ideas between the "users", AGF, and the Ordnance Department, in that Ordnance could suggest new equipment and propose new designs to AGF, while AGF could ask Ordnance to design or produce ideas to meet their requirements. There was a secondary line of communication between the Ordnance Department and overseas theatres of war on a similar basis. Within AGF, the Armored Force Board looked after tank matters. Approval for fundings for procurement .of new equipment meanwhile had to come from ASF. It is essential to appreciate these relationships (presented here in much simplified form) in order to understand many of the references to them in development histories of the later American vehicles.
In theory this organisation was perfectly simple, but as in Britain there was frequent friction between the "users" and the "suppliers", generally involving the forces of change in the form of the designers in the Ordnance Department against the forces of conservatism in the form of the Generals in Army Ground Forces. Notably there was the persistent work by the Ordnance Department to get heavier tanks than the M4 medium into service with more powerful guns. This was equally persistently opposed by AGF, who were content with M4s and 75mm guns. Thus there was a considerable delay in getting improved tanks accepted with 76mm and 90mm guns, the M26 Pershing, for example, only finally being sent to Europe when AGF were overruled by the General Staff after the Ardennes offensive by the Germans in December 1944. As events showed, however, the Ordnance Department was generally right in predicting the need for heavier guns and thicker armour years before Army Ground Forces found out the hard way in Europe in 1944. Generally speaking the US Ordnance Department did good work in 1940-45 producing a series of fine designs which, if not outstanding by German standards, proved to be adequate, and could be produced in such numbers as to sway the balance decisively in the favour of the Allies when it came to the final reckoning.
This summary cannot close without mention of the mammoth harnessing of American industry to the tank production programme. The setting up of the vast tank arsenals by major commercial companies on behalf of the US Government is recounted in detail later. It only remains to point out that the Ordnance Department acted as an agency for the co-ordination of the firms involved and in this respect were analagous to the British Department of Tank Design in dealings with commercial firms. However, Ordnance kept a firm hold of the actual design work. So great was industrial involvement with American tank production, that the Ordnance Department set up a special office in Detroit, OCO-D, specially to deal with tank design work right on the doorstep of the production facilities.