consistent with the German tactics of the previous three months, Allied intelligence had not understood that the strategy of fighting retreat had been for the sole purpose of providing time to prepare the Gustav line where the Germans intended to stand firm. The intelligence assessment of Allied prospects was therefore over-optimistic. The Fifth Army had only reached the Gustav Line on 15 January, having taken six weeks of heavy fighting to advance the last through the Bernhardt Line positions, during which time they had sustained 16,000 casualties. They hardly had time to prepare the new assault, let alone take the rest and reorganization they really needed after three months of attritional fighting north from Naples. However, because the Allied Combined Chiefs of Staff would only make landing craft available until early February, as they were required for Operation Overlord, the Allied invasion of Northern France, Operation Shingle had to take place in late January with the coordinated attack on the Gustav Line some three days earlier. First assault: X Corps on the left, 17 January The first assault was made on 17 January. Near the coast, the British X Corps (56th and 5th Divisions) forced a crossing of the Garigliano (followed some two days later by the British 46th Division on their right) causing General Fridolin von Senger und Etterlin, commander of the German XIV Panzer Corps, and responsible for the Gustav defences on the south western half of the line, some serious concern as to the ability of the German 94th Infantry Division to hold the line. Responding to Senger's concerns, Kesselring ordered the 29th and 90th Panzergrenadier Divisions from the Rome area to provide reinforcement. There is some speculation as to what might have been if X Corps had had the reserves available to exploit their success and make a decisive breakthrough. The corps did not have the extra men, but there would certainly have been time to alter the overall battle plan and cancel or modify the central attack by the U.S. II Corps to make men available to force the issue in the south before the German reinforcements were able to get into position. As it happened, Fifth Army HQ failed to appreciate the frailty of the German position and the plan was unchanged. The two divisions from Rome arrived by 21 January and stabilized the German position in the south. In one respect, however, the