2. The _most effectual_ mode of protecting the flank of a line or column of cavalry is by means of squadrons in rear, formed in echelons extending outwards; as this exposes the enemy's cavalry that may attempt to charge the main body in flank to be immediately charged in flank themselves; which would be destruction. For this purpose, irregular cavalry may be as effective as any other. 3. This cavalry support or reserve behind the flanks may sometimes play _an important offensive_ part. The enemy's first line, the instant after either making or receiving a charge, is always in greater or less disorder; and a vigorous charge then made on it in flank by our own flank reserve, would have a decisive effect. 4. Cavalry should never engage without a support or _reserve in rear_, not only to guard its flanks, but also to support it when disorganized by a successful charge. 5. So, when engaged in _skirmishing order_, being then very much exposed, it must always be protected, like infantry skirmishers, by supports in close order. 6. It has been already seen that, although cavalry may carry a position, it cannot hold it, if attacked by infantry. When used for such a purpose, therefore, it should always be accompanied by _an infantry support_. The French cavalry succeeded in carrying the plateau of Quatre Bras; but, having no infantry with it to reply to the terrible fire of the Allied infantry from the surrounding houses, it was compelled to retire, and yield it again to the enemy. According to Wellington, Napoleon frequently used his cavalry in seizing positions, which were then immediately occupied by infantry or artillery. V.--How Used. 1. Cavalry generally manoeuvres _at a trot_. At a gallop, disorder is apt to take place, and exhaustion of strength that will be needed in the charge. 2. The ordinary use of cavalry is to follow up infantry attacks and complete their success. It should never be sent _against fresh infantry_; and should generally, therefore, be reserved until towards the last of the action. Napoleon, who, by concentrating his cavalry into considerable masses, had enabled himself to use it on the battle-field as a principal arm, sometimes produced great effects by heavy cavalry charges at the very beginning of the action. But, though Napoleon's splendidly trained heavy cavalry might sometimes break a well-disciplined infantry without any preparatory artillery fire, it would be dangerous to attempt this with cavalry inferior to it in solidity; and the new rifled weapons would seem to render the cavalry charges of his day no longer practicable. 3. Cavalry _may_ be hurled against the enemy's infantry-- (1.) When it has been a long time engaged, and therefore exhausted. (2.) When it has been shattered by artillery. And _always should_ be-- (1.) When it is manoeuvring. (2.) When the attack would be a surprise. (3.) When its ranks begin to waver, or when it manifests any unequivocal symptom of hesitation or intimidation.