State volunteer forces were used extensively to augment the Regular Army throughout the 19th and early 20th century.
This concept was related to the idea of the brevet rank, which had generally fallen into disuse by the time of the First World War.
In September 1940, the United States reintroduced conscription in response to the increasing likelihood of entry into World War II.
[citation needed] The Army of the United States saw a major expansion following the 7 December 1941 attack on Pearl Harbor.
A typical situation might be a colonel in the AUS holding the permanent rank of captain in the Regular Army.
This was known as "loss of theater rank", with some instances of generals returning to the United States in disgrace or at least under a cloud, as only colonels or majors.
The system of prefixes before service numbers was as follows: The last use of the Army of the United States (AUS) was during the Vietnam War.
There is no equivalent to the Army of the United States in the U.S. Navy, Marine Corps, or Coast Guard.