These two bodies belong to that class of subjects into which both the tactical and strategic threads run simultaneously. On the one hand we must reckon them amongst those provisions which give form to the battle and ensure the execution of tactical plans; on the other hand, they frequently lead to independent combats, and on account of their position, more or less distant from the main body, they are to be regarded as links in the strategic chain, and it is this very feature which obliges us to supplement the preceding chapter by devoting a few moments to their consideration.
Every body of troops, when not completely in readiness for battle, requires an advanced guard to learn the approach of the enemy, and to gain further particulars respecting his force before he comes in sight, for the range of vision, as a rule, does not go much beyond the range of firearms. But what sort of man would he be who could not see farther than his arms can reach! The foreposts are the eyes of the army, as we have already said. The want of them, however, is not always equally great; it has its degrees. The strength of armies and the extent of ground they cover, time, place, contingencies, the method of making war, even chance, are all points which have an influence in the matter; and, therefore, we cannot wonder that military history, instead of furnishing any definite and simple outlines of the method of using advanced guards and outposts, only presents the subject in a kind of chaos of examples of the most diversified nature.
Sometimes we see the security of an army intrusted to a corps regularly appointed to the duty of advanced guard; at another time a long line of