The coming attack was much canvassed in Germany beforehand, and von Armin, having learned the lesson of his defeat at Messines, had prepared his defences. In Flanders the nature of the ground did not permit of a second Siegfried Line. Deep dug-outs and concreted trenches were impossible because of the water-logged soil, and he was compelled to find new tactics. His solution was the “pill-box.” These were small concrete forts, sited among the ruins of a farm or in some derelict piece of woodland, often raised only a yard or two above the ground level, and bristling with machine guns. The low entrance was at the rear, and the “pill-box” could hold from eight to forty men. It was easy to make, for the wooden or steel framework could be brought up on any dark night and filled with concrete. They were echeloned in depth with great skill, and, in the wiring, alleys were left so that an unwary advance would be trapped among them and exposed to enfilading fire. Their small size made them a difficult mark for heavy guns, and since they were protected by concrete at least three feet thick, they were impregnable to the ordinary barrage of field artillery. Von Armin’s plan was to hold his first line—which was often a mere string of shell craters—with few men, who would fall back before an assault. He had his guns well behind, so that they should not be captured in the first rush, and would be available for a barrage if his opponents became entangled in the “pill-box” zone. Finally, he had his reserves in the second line, ready for the counterstroke before the attack could secure its position. It will be seen that these tactics were admirably suited for the exposed and contorted ground of the Salient. Any attack would be allowed to make some advance; but if the German plan worked well, this advance would be short-lived and would be dearly paid for. Instead of the cast-iron front of the Siegfried area, the Flanders line would be highly elastic, but it would spring back into position after pressure with a deadly rebound. [Sidenote: _July 31._] The “preparation” for the battle lasted for the greater part of July, and every part of the Salient was drenched with our fire. On the last day of the month came the advance on a front of 15 miles—from the river Lys to a little north of Steenstraate, the main effort being that of the Fifth Army, under Sir Hubert Gough, on the 7½ miles between Boesinghe and the Zillebeke-Zandvoorde road. With the attack the weather broke. Gough’s purpose was to carry the enemy’s first defences, situated on the forward slope of the rising ground, and his second position along the crest. The opening day saw a brilliant success, for everywhere we captured the first line, and in many parts the second. But the weather prevented the series of cumulative blows which we had planned. For a fortnight we were compelled to hold our hand, since till the countryside grew dryer advance was a stark impossibility. [Sidenote: _Aug. 16._]