The Axis forces in Tunisia surrendered by May 1943, and Alexander's command became the 15th Army Group, which was, under General Eisenhower, responsible for mounting in July the Allied invasion of Sicily, again seeing Alexander controlling two field armies: General Montgomery's Eighth Army and Lieutenant General George S. Patton's U.S. Seventh Army. After Sicily, and in preparation for the Allied invasion of Italy, the Seventh Army headquarters were replaced by those of the U.S. Fifth Army, led by Lieutenant General Mark W. Clark.