During the summer months there was a strange quiet on the Eastern front. The German armies did not advance, though the way seemed plain before them. But they were not idle. Ludendorff had seen the opportunity afforded by the downfall of Russia, and believed that long before America took the field in strength he could deal a decisive blow to the Allies in the West. He prepared most patiently for this final _coup_, and turned the whole of his Eastern front into one vast training camp, where picked divisions were practised in open fighting; for his scheme demanded a high perfection of discipline and individual stamina. The history of the war had been the history of new tactical methods devised to break the strength of entrenched defences. The Allies had tried repeatedly from Neuve Chapelle onward, each time changing their plan, and at last at the Somme they seemed to have found a method which, though slow and laborious in its working, was decisive in its results. But the defection of Russia put an end to the hopes of this plan, and once again the theory of war was recast. But while Byng at Cambrai was feeling his way towards new tactics, Germany had already decided upon a scheme. She had seen that surprise was essential, and that therefore a laboured artillery “preparation” was out of the question. She realized, too, that in order to get the full cumulative effect of a blow, division must follow division to strike while the iron was hot. If these two things—surprise and an endless chain of troops of assault—could be found, then it might be possible to deal the decisive blow within the narrow limits of time still permitted to her. A break here and a break there meant only a restricted advance, behind which the enemy’s front grew solid in time, as concrete hardens with exposure. She therefore aimed not at a breakthrough in the older sense, but at a general crumbling.