Nor was the loss of life the only loss. These battles has led to a vast, and as it proved, wasteful expenditure of ammunition. Since the barrier could not be broken, the question now was how to render the envelopment scheme abortive by inflicting on the Allies losses which would delay or make impossible the offensive on the part of the Allies to which the scheme was designed to lead. Expedients to that end had to be devised more effective than the fire of heavy howitzers. They must also be less costly expedients. Thus hand grenades and trench mortars reappeared, and mechanical sniping. The reserve of shells with which Germany had begun the war was used up. Such munitions had to be employed more sparingly. Besides, owing to the scarcity of copper resulting from the British naval blockade, both the cost and the difficulty of manufacturing shells had immensely increased. The German ordinary grenade was nothing more than the small iron bomb which had been used during the campaigns in Flanders in the seventeenth century. It was now filled with a charge of guncotton, and hurled into the hostile trenches by hand. Another variety had attached to the globe a short iron stump. This enabled the grenade to be stuck on to the muzzle of a rifle, and fired into the opposing trenches when the distance was too great to allow of the use of hand bombs. The trench mortar fired in the same way an iron globular bomb about a foot in diameter. The bomb was stuck on to the muzzle of the mortar by a short iron stump projecting from it, and filled with a heavy charge of nitro-glycerine, was fired at a high angle, so that it might fall right into a hostile trench and by the tremendous force of the explosion wreck it. These projectiles, grenades and mortar bombs, were now turned out of the German arsenals in huge quantities. They were both much cheaper than shells, always a primary consideration in German warfare, and the mortar bombs required no copper driving bands. In addition to these expedients mines were resorted to. Several blind saps--tunnels slightly below the surface--driven towards a hostile line of trench would be connected by a cross tunnel, and in this just in front of the trench the mines would be laid. At the moment chosen for attack they would be exploded from the German position by electricity, and a rush made to occupy the craters so formed. Yet another ruse was to drive an open sap--a narrow zigzag cutting--to a point commanding a hostile trench, and there instal a machine gun. For daring in these operations military distinctions were freely bestowed, and it is not surprising that in carrying them out many of the enemy displayed an audacious cunning.