4th. That either of the last two may be employed in the offensive or defensive, according to the nature of the ground, the character of the general, and the character and position of the troops. Squares are always good against cavalry.

Troops should be habituated to all these formations, and accustomed to pass rapidly from one to another in the daytime or at night. None, however, but disciplined troops can do this: hence the great superiority of regulars on the field of battle, where skilful manœuvres frequently effect more than the most undaunted courage.

The arm next in importance on the battle-field is cavalry. The principal merit of this arm consists in its velocity and mobility. Cavalry has little solidity, and cannot of itself defend any position against infantry; but in connection with the other arms, it is indispensable for beginning a battle, for completing a victory, and for reaping its full advantage by pursuing and destroying the beaten foe.

There are four different modes of forming cavalry, the same as for infantry: 1st in deployed lines; 2d, a line of regiments in column of attack on the centre; 3d, the mixed formation; and 4th, the deep formation of several columns.

1st. The thin formation was deemed objectionable for infantry, on account of its liability to be penetrated by cavalry. The same objection does not hold so forcibly with respect to this latter arm; but full lines are deemed less advantageous than lines deployed checker-wise or in echelon. In either case the distance between the lines should be sufficient to prevent the second line from coming in contact with the first, in case the latter receives a slight check. This distance need not be so great in lines deployed checker-wise, as when they are full, or in echelon.

2d. The second system of formation, that is, a line of columns of attack on the central division for infantry, is by battalion, but for cavalry, by regiment. If the regiment is composed of eight squadrons, the column will contain four lines, two squadrons forming a division; but if composed of only six squadrons, the column will contain only three lines, and consequently will be six files in depth. In either case the distance between the lines should be that of a demi-squadron, when the troops are drawn up in battle array; but when charging, the divisions may close to a less distance.

3d. In forming a grand division of two brigades, by the third or mixed system, two regiments may be deployed in the first line, and three formed in columns of attack in rear of the flanks and centre, as is shown in [Fig. 33,] the sixth being held in reserve. This formation is deemed a good one.

4th. The fourth system, of deep columns of cavalry, is entirely unsuited for the charge, and this formation can only be employed for troops drawn up in reserve.

The flanks of lines or columns of cavalry are always much exposed, and squadrons should therefore be formed in echelon on the right and left, and a little in rear of the main body, in order to protect the flanks from the attacks of the enemy's horse. Irregular cavalry is usually employed for this purpose.

In the formation of a grand division in line of battle, care should be taken not to give too great an extent to the command of the generals of brigade. If the formation be in two lines, neither brigade should form an entire line, but each should form a wing of the division, two regiments of the same brigade being placed in rear of each other. This rule is an important one, and should never be neglected.