The XV Corps of the US Army was initially constituted on 1 October 1933 as part of the Organized Reserves, and was activated on 15 February 1943 at Camp Beauregard, Louisiana.

During the Second World War, XV Corps fought for 307 days in the European Theater of Operations, fighting from Normandy through France and southern Germany into Austria.

The corps headquarters was organized in January 1922 with Reserve personnel as a "Regular Army Inactive" (RAI) unit at Columbus, Ohio.

The XV Corps was not activated prior to World War II and was located in Indianapolis as of 7 December 1941 in an inactive reserve status.

In a controversial decision by the Twelfth United States Army Group commander, Lieutenant General Omar Bradley, the corps was halted at Argentan on 13 August 1944, before it could link up with Canadian troops, allowing Germans trapped in the Falaise Pocket an escape route to the east.

This breakthrough unbalanced German defenses in the northern Vosges and opened the way for Seventh Army troops to advance into Alsace and reach the Rhine River.

During this period, XV Corps defended well, restored most of its original position by 7 January 1945, and assumed a defensive stance again until mid-February.

Subsequently, the corps rested and prepared for offensive action designed to breach the Siegfried Line and invade Germany.