Haig's offensive in Flanders, a catastrophe of a different sort, began in July. Several elements shaped the Third Battle of Ypres. The most important was Haig's unbending commitment to offensive action on the western front and his beHef that a decisive breakthrough was possible. That behef was bolstered by his conviction that Allied offensives were draining the Germans of men and supplies. Thus, if a spectacular victory was not yet in sight, Britain and France were nonetheless winning the war of attrition. A second element, the growing threat of the submarine, made the capture of the Belgian coast, with its nest of U-boat bases, seem imperative. Finally, Britain's still potent forces were the only means available to divert German attention from the areas held by the perilously weak French army. As at the Somme, Haig relied upon a prolonged artillery bombardment followed by a massive infantry advance. As always on the western front, the artillery effort alerted the enemy to the area in which the assault was to occur. Beyond the skilled German defense, the British faced a still greater obstacle: the muddy terrain of Flanders. Haig had selected for his offensive a region subject to flooding. The rains of August 1917 combined with the artillery's destruction of the prewar drainage system to create a muddy hell in which effective advances were impossible and vast casualties inevitable. A temporary dry spell in September was followed by even heavier rain—and even more dismal hopes for a successful offensive—in October. The rationale for Haig's continuing efforts became less and less convincing. By the time of the greatest losses in the fall, Petain had gotten the French army over the worst of its indiscipline. Besides, the submarine bases were hopelessly out of reach, and the bases for the most dangerous submarines were not in Belgium but along Germany's northern coast. Unlike the French army under Nivelle, Haig's forces maintained their discipline in these impossible conditions. But the fighting capacity of the British army inevitably wavered as it suffered losses estimated somewhere between 250,000 and 400,000 men. Journalist Philip Gibbs, soon after the war's conclusion, recalled the battle's psychological cost: "For the first time the British Army lost its spirit of optimism, and there was a sense of deadly depression among many officers and men with whom I came in touch.