When the National Defense Act was adopted in June 1920, the Regular Army contained about 200,000 soldiers, roughly two-thirds the maximum authorized strength. In January 1921 Congress directed a prompt reduction in enlisted strength to 175,000 and in June 1921 decreased that figure to 150,000. A year later Congress limited the Regular Army to 12,000 commissioned officers and 125,000 enlisted men, not including the 7,000 or so in the Philippine Scouts; Army strength stabilized at about that level until 1936.
...
Despite its limited size, the Regular Army still deserved international respect. Foreign observers rated its recently established, newly equipped Air Corps second or third in actual power. But the Air Corps small inventory of modern equipment offered a marked contrast to the rest of the Army, where ground units had to get along as best they could for almost two decades with weapons left over from World War I. The Army was well aware that these old weapons were becoming increasingly obsolete. In 1933 General MacArthur described the Armys tanks, with the exception of a dozen experimental models, as completely useless for employment against any modern unit on the battlefield.
...
For a number of years only about a quarter of the officers and half of the enlisted men of the Regular Army were available for assignment to tactical units in the continental United States. Many units existed only on paper; almost all had only skeleton strength. The Regular Armys nine infantry divisions possessed the combined strength of only three full divisions. In May 1927 one of those undermanned infantry divisions, a cavalry brigade, and 200 aircraft participated in a combined-arms maneuver in Texas; but for the most part Regular Army units had to train as battalions or companies.