This is a historical narrative of the Third Infantry Division's experiences at the Anzio-Nettuno beachhead from 22 January to 2 June 1944. It identifies major contributing factors to the Third Infantry Division's battlefield success at the battle of Anzio-Nettuno. The battle is broken down into five distinct stages and investigated in a chronological manner. Potentially significant factors are evaluated in each stage of the battle and include terrain, weather, Allied air superiority, and the quality of military intelligence available to the Third Infantry Division's commander. Also compared for each side are the quality of senior leadership, previous combat experience, the quality and quantity of manpower replacements, and available artillery resources. This thesis concludes that the Third Infantry Division's battlefield success at Anzio-Nettuno appears to have been, to a large extent, a result of the quality and stability of the division's senior leadership, failures and missteps on the part of the higher German command echelons, the division's masterful employment of field artillery, and a highly effective training program.