On September 20, 1943, Lucas was given command of VI Corps, taking over from Major General Ernest J. Dawley. He led the corps in the early stages of the Italian Campaign, coming under command of the Fifth United States Army, commanded by Lieutenant General Mark Clark, who was many years younger. VI Corps crossed the Volturno Line in October and was involved in severe mountain warfare fighting until December when the corps HQ was pulled out of the line in preparation for an amphibious assault, codenamed Operation Shingle.