Early in the war, various schemes were devised for destroying the entanglements. There were bombs in the form of a rod about twelve feet long, which could be pushed under the wire and upon exploding would tear it apart. Another scheme was to fire a projectile formed like a grapnel. The projectile was attached to the end of a cable and was fired from a small gun in the same way that life-lines are thrown out to wrecks near shore. Then the cable would be wound up on a winch and the grapnel hooks would tear the wire from its fastenings. Such schemes, however, did not prove very practicable, and it was eventually found that a much better way of destroying barbed wire was to bombard it with high-explosive shell, which would literally blow the wire apart. But it required a great deal of shelling to destroy these entanglements, and it was really not until the tank was invented that such obstructions could be flattened out so that they formed no bar to the passage of the soldiers. The Germans not only used fixed entanglements, but they had large standard sections of barbed wire arranged in the form of big cylindrical frames which would be carried easily by a couple of men and could be placed in position at a moment's notice to close a gap in the line or even to build up new lines of wire obstruction. MINES AND COUNTER-MINES In the earlier stages of the war it proved so impossible to capture a trench when it was well defended by machine-guns that efforts were made to blow up the enemy by means of mines. Tunnels were dug reaching out under the enemy's lines and large quantities of explosives were stored in them. At the moment when it was intended to make an assault, there would be a heavy cannonading to disconcert the enemy, and then the mine would be touched off. In the demoralizing confusion that resulted, the storming-party would sweep over the enemy. Such mines were tried on both sides, and the only protection against them was to out-guess the other side and build counter-mines.