"It does not come within the view of this work to say any thing of the merely mechanical part of the art; because it must be taken for granted, that every man who accepts the command of an army knows at least the alphabet of his trade. If he does not, (unless his enemy be as ignorant as himself,) defeat and infamy await him. Without understanding perfectly what are called the evolutions, how is it possible that a general can give to his own army that order of battle which shall be most provident and skilful in each particular case in which he may be placed? How know which of these evolutions the enemy employs against him? and, of course, how decide on a counter-movement which may be necessary to secure victory or avoid defeat? The man who shall take the command of an army without perfectly understanding this elementary branch, is no less presumptuous than he who should pretend to teach Greek without knowing even his letters. If we have such generals, let them, for their own sakes, if not for their country's, put themselves immediately to school."
A battle is a general action between armies. If only a small portion of the forces are engaged it is usually denominated a combat, an affair, an action, a skirmish, &c., according to the character of the conflict. The art of combining and conducting battles of all descriptions has been designated by the name of Grand Tactics.
Battles may be arranged into three classes; 1st. Defensive battles, or those given in a chosen position by an army waiting the attack of the enemy. 2d. Offensive battles, or those made by an army which attacks the enemy in position. 3d. The mixed or unforeseen battles, given by two armies meeting while on the march.
I. When an army awaits the attack, it takes its position and forms its line of battle according to the nature of the ground and the supposed character and strength of the enemy's forces. Such is usually the case when an army wishes to cover a siege, protect a capital, guard dépôts of provisions and military stores, or some important strategic point. The general relations of positions with strategy and engineering have already been considered; we will now discuss merely their relations to battles.
The first condition to be satisfied by a tactical position is, that its debouches shall be more favorable for falling on the enemy when he has approached to the desired point, than those which the enemy can have for attacking our line of battle. 2d. The artillery should have its full effect upon all the avenues of approach. 3d. We should have good ground for manœuvring our own troops unseen, if possible, by the enemy. 4th. We should have a full view of the enemy's manœuvres as he advances to the attack. 5th. We should have the flanks of our line well protected by natural or artificial obstacles. 6th. We should have some means of effecting a retreat without exposing our army to destruction.
It is very seldom that all these conditions can be satisfied at the same time; and sometimes the very means of satisfying one, may be in direct violation of another. A river, a forest, or a mountain, which secures a flank of a line of battle, may become an obstacle to a retreat, should the defensive forces be thrown back upon that wing. Again, the position may be difficult of attack in front or on the wings, and at the same time unfavorable for retreat. Such was Wellington's position at Waterloo. The park of Hougomont, the hamlet of Haye Sainte, and the marshy rivulet of Papelotte, were serious obstacles against the attacking force; but the marshy forest of Soignies in rear, with but a single road, cut off all hope of retreat.
II. According to the strategic relations of the contending forces in a campaign, will it be determined whether we are to await the enemy, or to seek him out and attack him wherever he may be found. We may sometimes be obliged to make the attack at all hazards, for the purpose of preventing the junction of two corps, or to cut off forces that may be separated from the main body by a river, &c. As a general rule the attacking force has a moral superiority over the defensive, but this advantage is frequently more than counterbalanced by other conditions.
The main thing in an offensive battle is to seize upon the decisive point of the field. This point is determined by the configuration of the ground, the position of the contending forces, the strategic object of the battle; or, by a combination of these. For example, when one wing of the enemy rests on a height that commands the remainder of his line, this would seem the decisive point to be attacked, for its occupation would secure the greatest advantages; but this point may be so very difficult of access, or be so related to the strategic object as to render its attack out of the question. Thus it was at the battle of Bautzen: the left of the allies rested on the mountains of Bohemia, which were difficult of attack, but favorable for defence; moreover, their only line of retreat was on the right, which thus became the point of attack for the French, although the topographical and tactical key of the field was on the left.
III. It frequently happens in modern warfare that battles result from the meeting of armies in motion, both parties acting on the offensive. Indeed, an army that is occupying a defensive position may, on the approach of the enemy, advance to meet him while on the march. Battles of this kind may partake of the mixed character of offensive and defensive actions, or they may be of the nature of a surprise to both armies. To this class belong the battles of Rosbach, Eylau, Lutzen, Luzzara, Abensberg, &c.