The main strength, the actual spine of the position, so far as the British front was concerned, was some twenty-five miles of high ground forming the water-shed between the Somme and the rivers of southern Belgium, which ran, roughly, from Maricourt in the south, where our line joined the French, to Gomiecourt in the north. Here the enemy had sat untroubled for two years, looking down upon France and daily strengthening himself. His trebled and quadrupled lines of defence, worked for him by his prisoners, ran below and along the flanks and on the tops of five-hundred-foot downs. Some of these were studded with close woods, deadlier even than the fortified villages between them; some cut with narrowing valleys that drew machine-gun fire as chimneys draw drafts; some opening into broad, seemingly smooth slopes, whose every haunch and hollow covered sunk forts, carefully placed mine-fields, machine-gun pits, gigantic quarries, enlarged in the chalk, connecting with systems of catacomb-like dug-outs and subterranean works at all depths, in which brigades could lie till the fitting moment. Belt upon belt of fifty-yard-deep wire protected these points, either directly or at such angles as should herd and hold up attacking infantry to the fire of veiled guns. Nothing in the entire system had been neglected or unforeseen, except knowledge of the nature of the men, who in due time, should wear their red way through every yard of it. Neither side attempted to conceal their plans. The work of our airmen would have been enough to have warned the enemy what was intended, even had his own men overlooked the immense assembly of troops and guns in a breadth of country that had been remodelled for their needs, above ground and below. Our battalions in the Salient, where the unmolested German aeroplanes bombed them, knew well enough that, in the phrase of the moment, “everything had gone south,” and our listening-posts in the front line round Ypres could tell very fairly when a German “demonstration” was prompted by natural vice or orders to cover a noisy withdrawal of their guns in the same direction. It did not need placards in English, “Come on, we are ready for you!” which were hoisted in some of the German trenches on that Somme front to make men wiser than they had been for weeks past.