After a brief rest, the division was part of the amphibious landing at Anzio, codenamed Operation Shingle, on 22 January 1944, still as part of VI Corps, and serving alongside the British 1st Infantry Division and other units. It would remain there for just under four months in a toe-hold against numerous furious German counterattacks, and enduring trench warfare similar to that suffered on the Western Front during World War I. On 29 February 1944, the 3rd Division fought off an attack by three German divisions, who fell back with heavy losses two days later. In a single day of combat at Anzio, the 3rd Infantry Division suffered more than 900 casualties, the most of any American division on one day in World War II. The division's former commander, Major General Lucas, was replaced as commander of VI Corps by the 3rd Division's commander, Major General Truscott. He was replaced in command of the 3rd Division by Brigadier General John W. "Iron Mike" O'Daniel, previously the assistant division commander (ADC) and a distinguished World War I veteran.