When it's an "involuntary mobilization" of guys who've fulfilled their military obligation through the reserve program, but in whom the U.S. Army still has its hooks.
Reuters is reporting that the Pentagon will announce tomorrow that it intends to rope back into active service some 5,600 reservists who THOUGHT their obligations had been fulfilled. A defense department official told Reuters that while soldiers in the "Individual Ready Reserve" have served their voluntary obligation in the Army, they still can be mobilized involuntarily for several years after returning to civilian life.
In a notable understatement, Reuters said "The move ... represents the latest evidence of the strain being placed on the U.S. military, particularly the Army, by operations in [Afghanistan and Iraq]." They might have said "mismanagement" rather than "strain," but that would have been too obvious.