The British had discovered the futility of attempting to smash through the German lines without an adequate supply of high-explosive shells with which to destroy the heavy wire entanglements. Moreover, in maintaining a curtain of fire between the German lines and potential reenforcements, it was necessary to increase the artillery arm of the service. At this time the Germans could fire four shells to one by the British. Another very essential equipment in which the British were lacking was machine guns. The German army had developed machine-gun warfare apparently to its highest power. They not only used it to increase their volume of fire, but also as a means of saving their infantry. When, for any reason, it was found expedient to move infantry, a few machine-gun crews would take the place of the soldiers with the rifle and maintain a fire which would be almost as effective in checking the British advance as the infantry had been. The British had no such number of machine guns. They lacked this necessary part of their equipment just as they lacked shells, cannon, aircraft, and other war material which the Germans had developed and accumulated in large quantities under the supervision of the German General Staff. The German munition factories had been making and storing enormous supplies for an army of several millions of men. On the other hand the British had believed in the excellence of their comparatively small army to such an extent that it required all of the fighting from the time their troops landed on the Continent up to Festubert to convince them that they must make and maintain a military machine at least equal, if not superior, to the one her foes possessed. It is true the British needed more men in the ranks, but what was needed more was large additions to the supply of machine guns, artillery, and ammunition. For those reasons the British generals avoided clashes with the Germans after the battle of Festubert, except when it was necessary to hold as many of the Germans as possible to the British part of the western front. This plan was maintained throughout the summer of 1915. In the meantime the Germans were constructing, beyond their trenches, the most elaborate series of field fortifications in the history of warfare. The German staff realized that the time was coming when the British would again take the offensive. When that time arrived the Germans would thus be prepared to make every foot of ground gained as costly as possible to their foes. In fact they had reason for believing that it would be almost impossible for their opponents to gain ground where it was held by such seemingly impregnable works.