On War

by Carl von Clausewitz

The first is to be found in the alteration in tactics. A whole army is no longer led into battle as one body by mere word of command, to settle the affair like a great duel by more or less skill and bravery; the combatants on each side now range their forces more to suit the 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 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.

3. Because, although a corps thrown forward in front of the centre does not directly protect the wings as a real vanguard, it still contributes greatly to their security indirectly. For instance, the enemy cannot in ordinary cases pass by such a corps within a certain distance in order to effect any enterprise of importance against one of the wings, because he has to fear an attack in flank and rear. Even if this check which a corps thrown forward in the centre imposes on the enemy is not sufficient to constitute complete security for the wings, it is at all events sufficient to relieve the flanks from all apprehension in a great many cases.

The van-guard of the centre, if much stronger than that of a wing, that is to say, if it consists of a special corps as advanced guard, has then not merely the mission of a van-guard intended to protect the troops in its rear from sudden surprise; it also operates in more general strategic relations as an army corps thrown forward in advance.