From October to December 1943 VI Corps was involved in a bruising and bloody slog advancing from Naples up the Italian peninsula against the determined rearguard defence of the German 10th Army which skillfully took great advantage of the favorable terrain in organising successive lines of prepared defenses (Volturno Line, Barbara Line and Bernhardt Line). At the end of December, after heavy fighting on the Bernhardt Line (the forward defenses of the formidable Winter Line defenses) without a breakthrough, VI Corps was taken out of the line in an attempt to find a solution to the problem. In its second amphibious assault of the war, it came ashore at Anzio, south of Rome in Operation Shingle in January 1944 which was planned to threaten the rear lines of supply and communication of the German 10th Army. At first German resistance was negligible. However, Major General Lucas felt he needed to consolidate his beachhead before breaking out. This gave the Germans critical time to concentrate forces against him. Another bloody stalemate ensued, with the corps almost being driven back into the sea for the second time in Italy, again being rescued by naval and air power. When the stalemate was finally broken in the spring of 1944, the corps had lost another commander; Lucas was sacked for his poor performance and replaced by Major General Lucian Truscott, previously the commander of the 3rd Infantry Division. VI Corps also commanded units of the British Army during its time at Anzio, the British 1st Infantry Division, from 20 January until 21 May, and the British 2nd Commando Brigade and later, in mid-February, the British 56th Infantry Division and, from late March until 22 May, the British 5th Infantry Division.