Tac'tics, the science and art of conducting a battle. MILITARY TACTICS. Three different arms of the service, each complete in itself, are to be used separately and in combination (See INFANTRY; CAVALRY; ARTILLERY). Infantry is slow in its movements, but gives a resistless rifle fire and can be used where neither cavalry nor artillery can advance. At a distance of 900 yards, modern rifle fire is decisive, but it can be used to some effect at a distance of over one and a half miles. It is customary for infantry to advance in columns until they reach the zone of firing, and then to spread into a single, open-order line, so that a volley may not be so destructive. Each subdivision has been assigned, before entering action, a definite part of the enemy's lines as its target; but the range not being known, it must be assumed. The advance of the infantry is usually by short rushes, under the protection of rough ground, trees, buildings or whatsoever may be used to advantage. Between advances the men lie down behind ridges or hastily built defenses of earth and deliver their fire, either in volleys or in a certain number of rounds at will. Each man must think for himself, as it is impossible to keep any definite formation. At a distance of 900 yards, as has been said, the advance is usually broken, or the defenders are forced to retreat from their position. All the time while leading up to this climax of the battle, a steady fire has been kept up, and the line of the enemy has been continually searched for weakened spots, on which the fire might be concentrated. It often happens that in the ardor of an infantry charge, the men are carried to close quarters with the enemy and even scale the wall of the defense, especially when it has been weakened or broken by artillery fire. Cavalry has its chief advantage in its swiftness, and its chief use, therefore, is before the main battle or after the climax has passed, in pursuing a retreating enemy or in covering the retreat of its friends. If the main battle is on an open plain, cavalry can advance at will, but it forms an easy target for the enemy's artillery and could not, while armed only with swords and lances, be relied upon to defeat a strong infantry force. When cavalry meets cavalry, the first shock usually is decisive, though sometimes a hand-to-hand conflict follows, in which individual prowess wins. Sometimes cavalry makes a successful dash against artillery, particularly if it can reach the rear and unprotected side of the batteries. The cavalry usually acts in cooperation with the artillery and follows up by its charges the effective work of the great guns. Field artillery cannot protect itself on the flanks nor change position without pausing in its fire, and accordingly it is oftentimes at a disadvantage; but when placed properly and well served, it is an indispensable thing in the opening of a battle, where its great powers of destruction pave the way for the infantry and cavalry. Moreover, it forms the most effective cover for the retreat of its own army. Field guns are usually placed on a height, with a wide outlook, or they may be concealed behind a hill or obstruction, where, by an indirect fire over this protection, they reach the enemy. The first shots are experimental, but the officers observe the direction and range through their field glasses, and they direct the aim for more accurate marksmanship. No other branch of the service requires such careful drill, for the artilleryman must not only handle his gun with skill, but the officers must understand thoroughly the theory of projectiles, must be able to put this theory in practice and must show good judgment in the location of batteries and in the direction of the fire. After all, there are many elements, besides the general effectiveness of the three arms of the service, that enter into the decision of a modern battle. The personnel of the officers, the careful preparation, the element of surprise in the enemy's movements and the unknown conditions of ground, all call for well-balanced judgment and quick decision on the part of the commanders. The spirit and training of the troops, the relation between them and the subordinate commanders and the health of the men, are also important factors. NAVAL TACTICS. As in land operations, the commander in a battle at sea tries to hold off the enemy at every point, and so to overmatch him in one particular place that the line of battle can be broken. If once, in a sea fight, the line of battle is broken, it gives a much better opportunity than in land combat to destroy the disordered forces. The invention of steam changed the whole form of naval tactics, because it then became unnecessary to maneuver for the wind; and the continued improvements in naval artillery practically did away with the necessity of meeting at close quarters. The invention of the Monitor and other ironclads made the wooden vessel of little importance; and more recently the torpedo boats and submarines have made the life of even the giant battleship insecure. In a modern sea fight all the various ships, each armed in its own peculiar way, must be maneuvered so as to use its points to the greatest advantage, guarding its weaknesses and taking advantage of its points of superiority wherever possible. The sea affords no shelter for troops and gives little opportunity for concealing the size of the forces or the plan of battle. Some vessels are so arranged that they can fire straight ahead or astern, rather than broadside, and such ones are used in a way to profit by that quality. But in the majority of cases the greatest power of a vessel is in its broadside fire, as every vessel avoids, if possible, being struck by shot which travel its entire length. Ships in battle usually pass each other in column; if two alone be fighting, both sail in circles; if the attack is made against coast defense or against a stationary fleet, all sail in the form of an ellipse, these maneuvers bringing the most guns into action to the best advantage. Close quarters are always avoided, for fear of torpedoes, which consequently are used chiefly at night. The great warships are rather unwieldy, as they cannot be stopped or turned in several times their own length, so that it is dangerous to change speed or formation in the heat of battle. In the United States navy, a fleet is divided into squadrons of from two to eight ships; a division is half a squadron of six ships or more, and a section is made up of two ships of a squadron. When all the ships of a fleet are advancing abreast, they are said to be arranged in line; they are in column when they advance in single file, and they are in echelon when all advance along a course diagonal to the line which would pass through all the ships.