Eight days after the Allied invasion of mainland Italy, on 18 September 1943, the 3rd Division came ashore at Salerno, where they came under the command of VI Corps, under Major General Ernest J. Dawley who was replaced two days later by Major General John P. Lucas (who had commanded the division from September 1941 to March 1942). The corps was part of Lieutenant General Mark W. Clark's U.S. Fifth Army. The 3rd Division was destined to see some of the fiercest and toughest fighting of the war thus far, serving on the Italian Front. Seeing intensive action along the way, the division drove to and across the Volturno River by October 1943, and then to Monte Cassino, where the Battle of Monte Cassino would later be fought, before, with the rest of the 15th Army Group, being held up at the Winter Line (also known as the Gustav Line). In mid-November the division, after spearheading the Fifth Army's advance and suffering heavy casualties during the past few weeks, was relieved by the 36th Infantry Division and pulled out of the line to rest and absorb replacements, coming under the command of Major General Geoffrey Keyes' II Corps. The division remained out of action until late December.