peculiarities of the ground and circumstances, so that the order of battle, and consequently the battle itself, is a whole made up of many parts, from which there follows, that the simple determination to fight becomes a regularly formed plan, and the word of command a more or less long preparatory arrangement. For this time and data are required.
The second cause lies in the great size of modern armies. Frederick brought thirty or forty thousand men into battle; Napoleon from one to two hundred thousand.
We have selected these examples because every one will admit, that two such generals would never have adopted any systematic mode of proceeding without some good reason. Upon the whole, there has been a general improvement in the use of advanced guards and outposts in modern wars; not that every one acted as Frederick, even in the Silesian wars, for at that time the Austrians had a system of strong outposts, and frequently sent forward a corps as advanced guard, for which they had sufficient reason from the situation in which they were placed. Just in the same way we find differences enough in the mode of carrying on war in more modern times. Even the French Marshals Macdonald in Silesia, Oudinot and Ney in the Mark (Brandenburg), advanced with armies of sixty or seventy thousand men, without our reading of their having had any advanced guard.—We have hitherto been discussing advanced guards and outposts in relation to their numerical strength; but there is another difference which we must settle. It is that, when an army advances or retires on a certain breadth of ground, it may have a van and rear guard in common for all the columns which are marching side by side, or each column may have one for itself. In order to form a clear idea on this subject, we must look at it in this way.
The fundamental conception of an advanced guard, when a corps is so specially designated, is that its mission is the security of the main body or centre of the army. If this main body is marching upon several