My understanding is that the first is the common usage, and the second is a slightly more formal usage (and/or slightly archaic). However, a friend who served as an infantry lieutenant late in WW2 distinctly recalls being told by a superior officer that the first is reserved for those officers graduating from West Point, while the second was for those who came up through OCS or other programs. He’s a great guy, but I’m dubious.
Is there any practical or substantive distinction between the phrases now?
Forces drafted, in this case for the Second World War, are termed the “Army of the United States” for the duration of the draft. His was a career-versus-draft distinction.
The United States Army (USA) is the regular army. If you go down to the recruiting office and enlist you join the US Army.
The Army of The United States (AUS) is a temporary organization established to allow a temporary, rapid, and large, increase in the size of the army in case of a general way that the Regular Army isn’t big enough to handle. It allows this increase without committing the government to maintain such an army and officer corps after the war ends. The total authorized strength of the USA isn’t increased and all enlistments, promotions, etc. are only for the duration of the war and a certain period following. When you enlist in the regular army you and the government agree to a contract and neither side can get out of it, at least as long as the enlistee continues to meet the requirements.
During such a war, if you enlist you enlist in the Army of The Unites States. You do not accumulate time for retirement and all promotions are temporary. At the time of such a war, members of the US Army are also taken into the AUS and their promotions in the AUS are also temporary. It is possible for a regulary army member to have to ranks, one, say Master Sgt., in the AUS and another, say corporal, in the USA.
The article says that the AUS consisted of those drafted. However it also included those who enlisted volunarily. When I enlisted in 1942 my enlistment was in the AUS.
USMA graduates used to receive commissions in the Regular Army and ROTC graduates received commissions in the Army Reserve. In recent years, the Army has made policy changes that eliminate that distinction, so that all junior officers compete for promotion and commissions in the Regular Army.