Once in Britain the division was attached to U.S. XVIII Airborne Corps, under Major General Matthew Ridgway, which commanded all American airborne formations, and which in turn became part of the First Allied Airborne Army when it was formed on 21 August, under the command of Lieutenant General Lewis H. Brereton. Although attached to XVIII Airborne Corps, the division was not chosen to participate in Operation Market Garden, a large-scale airborne operation intended to seize several bridges through the Netherlands to allow the Allied armies to bypass the Rhine river and enter Germany. The 17th was passed over in favour of the 82nd and 101st Airborne Divisions because it had only recently arrived in the European Theater and was considered to be unprepared logistically as it was still collecting its combat equipment. The division, now with Colonel Edson Raff's 507th Parachute Infantry Regiment under command–a veteran unit which had fought in Normandy under command of the 82nd Airborne Division–remained in England as a theater reserve during Market Garden and its aftermath, as the Allied armies continued their advance towards Germany.