The army that is standing still throws out lines of pickets in front to watch for the enemy’s advance and report it. The enemy, as he advances, also throws out a cloud of skirmishers to “feel” of the position and avoid traps and ambushes. A line of battle often extends over several miles in length, covering all available ground for attack or defence. Before the advancing general can determine against what part of his adversary’s line to hurl his heaviest battalions, he must study the conditions along that line; namely, by means of his skirmishers. In the same way the general who is awaiting attack tries to discover through his skirmishers what his enemy’s plan of battle is, and at what points he most needs to concentrate his own men. While awaiting this information he posts his men--cavalry, artillery, and infantry--wherever he thinks they will be most useful, having reference all the time to their rapid movement during the battle from one part of the line to another, as occasion may demand. He also holds a considerable part of his army “in reserve.” That is to say, he stations it at points a little in rear of the line of battle, from which he can order all or any part of it to any point where strength may be needed. In a great battle, involving large bodies of troops, each corps or division commander must do in a smaller way what the general-in-chief does on a larger scale. Each has charge of the battle on a certain part of the line. Each must take care of things within his own jurisdiction, and be ready at a moment’s notice to respond to the demand of the commanding general for troops with which to help out elsewhere. These are the generalities. Let us now come to the battle itself. When the skirmishers of the advancing army meet the skirmishers of the resisting army, there is apt to be some pretty hot fighting for a time, and sometimes the artillery is considerably involved in it. But this is not the real thing; it is a mere preliminary to the actual battle. The army that is standing on the defensive holds its lines in position--every battery placed where it will do the most good, and every infantryman lying down and taking the utmost advantage of every tree stump, log, or inequality of the ground, to protect himself as much as possible. The men on horseback are either in front with the skirmishers, minutely observing the strength and movements of the enemy, or, having finished that work, are thrown out at the two ends of the lines, called “flanks,” to watch there for possible movements of the enemy that might be otherwise unobserved. They are within call of any part of the line where need of them may arise. While the skirmishers are doing their work, the heaviest strain of war falls on the nerves of the men in line of battle. They have nothing to do but wait.