The Change in the Military Situation—Haig’s Plan for Third Ypres—The Nature of the Problem—Von Armin’s Defensive Tactics—The “Pill-boxes”—The Attack of 31st July—The Attack of 16th August—The British Front reorganized—The 9th Division enters the Salient—Its “Pill-box” Tactics—The Night Assembly—The Attack of 20th September—The Fall of Potsdam Redoubt—The First Objective gained—The Second Objective gained—The Difficulties on the Left Flank—The Result of the Battle—Individual Exploits—The Brigade’s Losses—The Field Ambulance Work—The Brigade returns to the Salient—Moves to the Belgian Coast—The Close of Third Ypres. When, on the last day of July 1917, Sir Douglas Haig launched his attack in the Ypres salient, the nature of the war had dramatically changed. The great plan conceived for 1917, of which the Somme had been the logical preliminary, had proved impossible. This was not due wholly or mainly to the failure of the ambitious offensive in April at Arras and on the Aisne. The real cause was the defection of Russia, for, by the failure of one great partner, the old military coherence of the Alliance had gone. The beleaguering forces which had sat for three years round the German citadel were wavering and straggling on the East. The war on two fronts, which had been Germany’s chief handicap, looked as if it might change presently to a war on a single front. Whatever victories might be won during the remainder of 1917, it was now certain that a decisive blow could not be delivered. The Teutonic League, just when it was beginning to crumble, had been given a new tenure of life. Up till then the campaign had been fought on data which were familiar and calculable. The material and human strength of each belligerent was known, and the _moral_ of each was confidently assessed. But with the Russian revolution new factors had suddenly appeared out of the void, and what had seemed solid ground became sand and quagmire. It was the old Europe which waged war up till the spring of 1917; but a new Europe had come into being by midsummer in which nothing could be taken for granted. Everywhere in the world there was the sound of things breaking.