The first is, if cavalry alone are employed; in that case it amounts usually more to alarming and watching than to pressing the enemy in reality, because the smallest obstacle of ground is generally sufficient to check the pursuit. Useful as cavalry may be against single bodies of broken demoralised troops, still when opposed to the bulk of the beaten Army it becomes again only the auxiliary arm, because the troops in retreat can employ fresh reserves to cover the movement, and, therefore, at the next trifling obstacle of ground, by combining all arms they can make a stand with success. The only exception to this is in the case of an army in actual flight in a complete state of dissolution. The second degree is, if the pursuit is made by a strong advance-guard composed of all arms, the greater part consisting naturally of cavalry. Such a pursuit generally drives the enemy as far as the nearest strong position for his rear-guard, or the next position affording space for his Army. Neither can usually be found at once, and, therefore, the pursuit can be carried further; generally, however, it does not extend beyond the distance of one or at most a couple of leagues, because otherwise the advance-guard would not feel itself sufficiently supported. The third and most vigorous degree is when the victorious Army itself continues to advance as far as its physical powers can endure. In this case the beaten Army will generally quit such ordinary positions as a country usually offers on the mere show of an attack, or of an intention to turn its flank; and the rear-guard will be still less likely to engage in an obstinate resistance. In all three cases the night, if it sets in before the conclusion of the whole act, usually puts an end to it, and the few instances in which this has not taken place, and the pursuit has been continued throughout the night, must be regarded as pursuits in an exceptionally vigorous form.