When the line E F begins to advance, its guns will bombard the position which it hopes to capture. They will also try to put out of action any guns firing on their troops, and will crush all attempts of the enemy's infantry to make a counter-attack. They thus prepare the way for an advance, and protect the advance while it is being made. If they are successful, their infantry will probably reach the goal in such condition that they can make a bayonet charge. When this time arrives the artillery cannot fire straight forward, because by so doing they will hit their own men. They therefore sweep the ground to the right and left in order to prevent the enemy from making flank attacks on the advancing force. When the position has been won the guns hurry up and begin the business all over again. Always remember that a battle is nothing but a great shooting match, in which both guns and rifles are used. [Illustration: Columns marching along three parallel roads and deploying.] Guns work in groups or batteries of six guns each, and three batteries form a brigade. If you see artillery on the march, you will notice that the guns and their wagons always follow each other, and never go two abreast. In battle the artillery form a line of guns, with about nineteen yards between gun and gun. Three men work each gun, and they are protected by a steel shield. The horses and drivers take cover some distance in the rear of the guns, but within easy reach of them. Artillery officers always try to secure a position in which their guns are not easily seen, and yet have in front of them a large area of open country over which they can direct their fire. * * * * * In addition to riflemen, horsemen, and gunners, an army needs other services in order to make it an effective fighting machine. For example, it needs engineers to remove those obstacles in its path which prevent it from advancing quickly and easily. Engineers make roads and light railways, bridge rivers, or blow up bridges in order to delay the enemy. They also make fortifications and set up telegraphs and telephones, so that a general may know what is going on in all parts of his line, and transmit his orders as quickly as possible to the various commanders. What is called a field company of Engineers is, roughly, of the same strength as an infantry company. It carries with it shovels for digging trenches, axes for cutting down trees, wire for making entanglements, sand-bags for protecting men firing from trenches, explosives, carpenters' and smiths' tools, water-supply stores, signalling apparatus, and the materials for making maps. All these things are carried in four-horsed carts and on the backs of pack animals. Six-horsed wagons are laden with the materials for building bridges, such as pontoons, trestles, planks, and so forth. An Engineer company can erect a bridge across a stream in a very short time, and take it down even more rapidly.