and it also possessed several faults. Its size limited the possible crew to three—a driver in the hull and a gunner and commander in the turret—which was found to be too few crew members to operate the Tetrarch effectively. The gunner or commander, in addition to his own duties, had to act as loader for the 2-pounder, which caused delays in combat; a report on the tank written in January 1941 stated that since the commander had both to fight and control the tank, controlling a troop of Tetrarchs during combat would be almost impossible. The War Office was also aware that the tank had a faulty cooling system that made the Tetrarch unsuitable for service in hotter climates, such as the Middle East and North Africa. A purpose-built airborne light tank was therefore required to replace the Tetrarch, but the decision was taken by the War Office not to produce the tank in Britain due to a lack of production capacity. Instead the American government was approached with a request that it produce a replacement for the Tetrarch. This request was made by the British Air Commission in Washington, D.C., with a proposal calling for a tank of between and to be developed, this being the maximum weight the War Office had decided could be carried by current glider technology. The proposed tank was to have a primary armament of a main gun and secondary armament of a .30-06 Browning M1919A4, and a crew of three. The specification also called for a maximum speed of and an operational radius of . The turret and front of the hull were to have an armour thickness of between and , and the sides of the tank a thickness of . The United States Ordnance Department was given the task of developing the proposed tank, and in turn requested designs from three American companies: General Motors, J. Walter Christie and Marmon-Herrington. The design offered by Christie in mid-1941 was rejected as it failed to meet the specified size requirements, as was a modified design the company produced in November. At a conference in May 1941, the Ordnance Department chose the Marmon-Herrington design and requested that the company produce a prototype tank, which was completed in late 1941; it was designated the Light Tank T9 (Airborne) by the company and the Ordnance Department. Development The T9 had a crew of three and weighed