general. As chief of staff from 1930 to 1935, MacArthur wanted to advance motorization and mechanization throughout the Army. In late 1931 all arms and services were directed to adopt mechanization and motorization, and were permitted to conduct research and experiment as necessary. The Cavalry was given the task of developing combat vehicles that would enhance its role of reconnaissance, counter-reconnaissance, flank action, and pursuit. With the law passed, tanks belonged to the infantry branch, so the cavalry gradually bought a group of combat cars, lightly armored and armed tanks that were often indistinguishable from the newer infantry "tanks". In 1933, MacArthur set the stage for the complete mechanization of the cavalry, declaring "The horse has no higher degree of mobility today than he had a thousand years ago. The time has therefore arrived when the Cavalry arm must either replace or assist the horse as a means of transportation, or else pass into the limbo of discarded military formations." In November 1936, the U.S. Army's cavalry branch decided to modernize and needed a fully armored vehicle, capable of keeping up with the cavalry and of fulfilling regular combat duties. Prohibited from developing tanks by the National Defense Act of 1920, it could not develop a "tank" in the conventional sense, so opted for a smaller and lighter "car" class vehicle. It came up with the T7 Combat Car, designed and built at the Rock Island Arsenal between 1937 and 1938, which was based on the M1 Combat Car but with an extended chassis and a convertible suspension - the ability to travel using wheels or tracks. The only prototype T7 Combat Car (No. W40223) was shipped to Aberdeen Proving Grounds in August 1938 for testing. While it showed good speed and performance, cavalry branch representatives were not impressed. Tests were delayed until 1939, but they were reasonably successful. The vehicle even participated in the First Army maneuvers at Plattsburgh, New York, in 1939, where the cavalrymen liked it. However, in October 1939, the cavalry branch formed new requirements for their combat vehicles which specified regular tracked (not combined) suspension. The reason for that decision was that the tracks were already available in reasonable quantity and quality and thus there was no need for the complexity and higher cost associated with convertible vehicles.[2] Furthermore, the heavy M2 Browning machine gun it was equipped with was determined insufficient for the role.