There were limits, however, to the German appreciation of the plans of the Allies. They were apparently convinced that the attack would come somewhat farther to the north, and their plans, which covered more than half of the ground on which the attack actually did occur, had made that region impregnable, as we were to learn to our cost. Their heaviest guns and their best troops were there. They had made a far less elaborate preparation, however, at the front which corresponded with the southern end of the British line, and also on that which faced the French. The reasons for this may be surmised. The British front at that point is very badly supplied with roads (or was before the matter was taken in hand), and the Germans may well have thought that no advance upon a great scale was possible. So far as the French were concerned they had probably over-estimated the pre-occupation of Verdun and had not given our Allies credit for the immense reserve vitality which they were to show. The French front to the south of the Somme was also faced by a great bend of the river which must impede any advance. Then again it is wooded, broken country down there, and gives good concealment for masking an operation. These {38} were probably the reasons which induced the Germans to make a miscalculation which proved to be an exceedingly serious one, converting what might have been a German victory into a great, though costly, success for the Allies, a prelude to most vital results in the future.