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 contiguous roads so close together that they can also easily serve for the advanced guard, and therefore be covered by it, then the flank columns naturally require no special covering. But those corps which are moving at great distances, in reality as detached corps, must provide their own van-guards. The same applies also to any of those corps which belong to the central mass, and owing to the direction that the roads may happen to take, are too far from the centre column. Therefore there will be as many advanced guards, as there are columns virtually separated from each other; if each of these advanced guards is much weaker than one general one would be, then they fall more into the class of other tactical dispositions, and there is no advanced guard in the strategic tableau. But if the main body or centre has a much larger corps for its advanced guard, then that corps will appear as the advanced guard of the whole, and will be so in many respects. But what can be the reason for giving the centre a van-guard so much stronger than the wings? The following three reasons. 1. Because the mass of troops composing the centre is usually much more considerable. 2. Because plainly the central point of a strip of country along which the front of an army is extended must always be the most important point, as all the combinations of the campaign relate mostly to it, and therefore the field of battle is also usually nearer to it than to the wings.