Walker commanded the 36th Division during the whole of its service in the grueling slog up Italy, crossing the Volturno Line in October, and by late November/early December, by which time the division was part of Major General Geoffrey Keyes' U.S. II Corps, were fighting in front of the Bernhardt Line, part of the formidable Winter Line defenses, suffering heavy casualties in the Battle of San Pietro Infine, later participating in the Rapido river crossing, part of the First Battle of Monte Cassino, and Mount Artemisio on the drive north through Rome and beyond. The fighting in the early months of the Allied campaign in Italy proved very costly for the 36th Division, due to determined German resistance, the mountainous terrain, and the worsening winter weather. Walker was critical of the leadership in Italy, writing, "The Italian campaign will not be finished this week, nor next. Our wasteful policy or method of taking one mountain mass after another gains no tactical advantage, locally. There is always another mountain mass beyond with the Germans dug in on it, just as before. Somebody on top side, who control of the required means, should figure out a way to decisively defeat the German army in Italy, instead of just pushing, pushing, pushing."