Second United States Army was formed October 15, 1918 during World War I. It functioned as a training and administrative headquarters until being inactivated 15 April1919.
The Second United States Army was activated again and served as a training army for much of its existence until inactivation in 1966.
On 10 November, Second Army advanced on German positions, already in disorder and retreating. Word did not reach the units advancing until after eleven-hundred hours on 11 November, making it one of the last units to fight to the very conclusion of the war. On 15 April of the following year, Second Army was inactivated.
In November 1964, as an effort to reorganize military operations, the Department of the Army announced the closure of Fort Jay at Governors IslandNew York and the relocation of U.S.First Army to Fort Meade, Maryland. First and Second Armies would merge and Second Army subsequently inactivated. It had been proposed that First Army be inactivated, but its commander Lt. General Robert W. Porter, Jr. strongly protested the proposal and it was dropped. In the end, Second Army headquarters staff were retained and became the new staff for U.S. First Army. On January 1, 1966 at Fort Meade, Second Army was inactivated and its colors cased by commander, Lt. General William F. Train who then assumed command of U.S. First Army.