Front Page Titles (by Subject) CHAPTER VII: ADVANCE GUARD AND OUTPOSTS - On War, vol. 2
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CHAPTER VII: ADVANCE GUARD AND OUTPOSTS - Carl von Clausewitz, On War, vol. 2 
On War, trans. Col. J.J. Graham. New and Revised edition with Introduction and Notes by Col. F.N. Maude, in Three Volumes (London: Kegan Paul, Trench, Trubner & C., 1918). Vol. 2.
Part of: On War
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ADVANCE GUARD AND OUTPOSTS
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 advance 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 outposts 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 advance 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 entrusted to a Corps regularly appointed to the duty of advance guard; at another time a long line of separate outposts; sometimes both these arrangements co-exist, sometimes neither one nor the other; at one time there is only one advance guard in common for the whole of the advancing columns; at another time, each column has its own advance guard. We shall endeavour to get a clear idea of what the subject really is, and then see whether we can arrive at some principles capable of application.
If the troops are on the march, a detachment of more or less strength forms its van or advance guard, and in case of the movement of the Army being reversed, this same detachment will form the rearguard. If the troops are in cantonments or camp, an extended line of weak posts, forms the vanguard, the outposts. It is essentially in the nature of things, that, when the Army is halted, a greater extent of space can and must be watched than when the Army is in motion, and therefore in the one case the conception of a chain of posts, in the other that of a concentrated body arises of itself.
The actual strength of an advance guard, as well as of outposts, ranges from a considerable Corps, composed of an organisation of all three arms, to a regiment of hussars, and from a strongly entrenched defensive line, occupied by portions of troops from each arm of the service, to mere outlying pickets, and their supports detached from the main camp. The services assigned to such vanguards range also from those of mere observation to an offer of opposition or resistance to the enemy, and this opposition may not only be to give the main body of the Army the time which it requires to prepare for battle, but also to make the enemy develop his plans, and intentions, which consequently makes the observation far more important.
According as more or less time is required to be gained, according as the opposition to be offered is calculated upon and intended to meet the special measures of the enemy, so accordingly must the strength of the advance guard and outposts be proportioned.
Frederick the Great, a General above all others ever ready for battle, and who almost directed his Army in battle by word of command, never required strong outposts. We see him therefore constantly encamping close under the eyes of the enemy, without any great apparatus of outposts, relying for his security, at one place on a hussar regiment, at another on a light battalion, or perhaps on the pickets, and supports furnished from the camp. On the march, a few thousand horse, generally furnished by the cavalry on the flanks of the first line, formed his advance guard, and at the end of the march rejoined the main body. He very seldom had any corps permanently employed as advance guard.
When it is the intention of a small Army, by using the whole weight of its mass with great vigour and activity, to make the enemy feel the effect of its superior discipline and the greater resolution of its Commander, then almost every thing must be done sous la barbe de l’ennemi, in the same way as Frederick the Great did when opposed to Daun. A system of holding back from the enemy, and a very formal, and extensive system of outposts would neutralise all the advantages of the above kind of superiority. The circumstance that an error of another kind, and the carrying out Frederick’s system too far, may lead to a battle of Hochkirch, is no argument against this method of acting; we should rather say, that as there was only one battle of Hochkirch in all the Silesian War, we ought to recognise in this system a proof of the King’s consummate ability.
Napoleon, however, who commanded an Army not deficient in discipline and firmness, and who did not want for resolution himself, never moved without a strong advance guard. There are two reasons for this.
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 advance 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 advance guard, for which they had sufficient reason from the situation in which they were placed. 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 advance guard.* —We have hitherto been discussing advance 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 advance 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 advance 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 vanguards. 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 advance guards as there are columns virtually separated from each other; if each of these advance 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 advance guard in the strategic tableau. But if the main body or centre has a much larger Corps for its advance guard, then that Corps will appear as the advance guard of the whole, and will be so in many respects.
But what can be the reason for giving the centre a vanguard 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 vanguard of the centre, if much stronger than that of a wing, that is to say, if it consists of a special Corps as advance guard, has then not merely the mission of a vanguard 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.
The following are the purposes for which such a body may be used, and therefore those which determine its duties in practice.
1. To ensure a stouter resistance, and make the enemy advance with more caution; consequently to do the duties of a vanguard on a greater scale, whenever our arrangements are such as to require time before they can be carried into effect.
2. If the central mass of the army is very large, to be able to keep this unwieldy body at some distance from the enemy, while we still remain close to him with a more movable body of troops.
3. That we may have a corps of observation close to the enemy, if there are any other reasons which require us to keep the principal mass of the Army at a considerable distance.
The idea that weaker look-out posts, mere bodies of partisan, might answer just as well for this observation is set aside at once if we reflect how easily a weak detachments might be dispersed, and how very limited also are its means of observation as compared with those of a considerable force.
4. In the pursuit of the enemy. A single corps as advance guard, with the greater part of the cavalry attached to it, can move quicker, arriving later at its bivouac, and moving earlier in the morning than the whole mass.
5. Lastly, on a retreat, as rearguard, to be used in defending the principal natural obstacles of ground. In this respect also the centre is exceedingly important. At first sight it certainly appears as if such a rearguard would be constantly in danger of having its flanks turned. But we must remember that, even if the enemy succeeds in overlapping the flanks to some extent, he has still to march the whole way from there to the centre before he can seriously threaten the central mass, which gives time to the rearguard of the centre to prolong its resistance, and remain in rear somewhat longer. On the other hand, the situation becomes at once critical if the centre falls back quicker than the wings; there is immediately an appearance as if the line had been broken through, and even the very idea or appearance of that is to be dreaded. At no time is there a greater necessity for concentration and holding together, and at no time is this more sensibly felt by every one than on a retreat. The intention always is, that the wings in case of extremity should close upon the centre; and if, on account of subsistence and roads, the retreat has to be made on a considerable width (of country), still the movement generally ends by a concentration on the centre. If we add to these considerations also this one, that the enemy usually advances with his principal force in the centre and with the greatest energy against the centre, we must perceive that the rearguard of the centre is of special importance.
Accordingly, therefore, a special Corps should always be thrown forward as an advance guard in every case where one of the above relations occurs. These relations almost fall to the ground if the centre is not stronger than the wings, as, for example, Macdonald when he advanced against Blücher, in Silesia, in 1813, and the latter, when he made his movement towards the Elbe. Both of them had three Corps, which usually moved in three columns by different roads, the heads of the columns in line. On this account no mention is made of their having had advance guards.
But this disposition in three columns of equal strength is one which is by no means to be recommended, partly on that account, and also because the division of a whole Army into three parts makes it very unmanageable, as stated in the fifth chapter of the third book.
When the whole is formed into a centre with two wings separate from it, which we have represented in the preceding chapter as the most natural formation as long as there is no particular object for any other, the Corps forming the advance guard, according to the simplest notion of the case, will have its place in front of the centre, and therefore before the line which forms the front of the wings; but as the first object of Corps thrown out on the flanks is to perform the same office for the sides as the advance guard for the front, it will very often happen that these Corps will be in line with the advance guard, or even still further thrown forward, according to circumstances.
With respect to the strength of an advance guard we have little to say, as now very properly it is the general custom to detail for that duty one or more component parts of the Army of the first class, reinforced by part of the cavalry: so that it consists of a Corps, if the army is formed in Corps; of a Division, if the organisation is in Divisions.
It is easy to perceive that in this respect also the great number of higher members or divisions is an advantage.
How far the advance guard should be pushed to the front must entirely depend on circumstances; there are cases in which it may be more than a day’s march in advance, and others in which it should be immediately before the front of the Army. If we find that in most cases between five and fifteen miles is the distance chosen, that shows certainly that circumstances have usually pointed out this distance as the best; but we cannot make of it a rule by which we are to be always guided.
In the foregoing observations we have lost sight altogether of outposts, and therefore we must now return to them again.
In saying, at the commencement, that the relations between outposts and stationary troops is similar to that between advance guards and troops in motion, our object was to refer the conceptions back to their origin, and keep them distinct in future; but it is clear that if we confine ourselves strictly to the words we should get little more than a pedantic distinction.
If an Army on the march halts at night to resume the march next morning, the advance guard must naturally do the same, and always organise the outpost duty, required both for its own security and that of the main body, without on that account being changed from an advance guard into a line of outposts. To satisfy the notion of that transformation, the advance guard would have to be completely broken up into a chain of small posts, having either only a very small force, or none at all in a form approaching to a mass. In other words, the idea of a line of outposts must predominate over that of a concentrated Corps.
The shorter the time of rest of the Army, the less complete does the covering of the Army require to be, for the enemy has hardly time to learn from day to day what is covered and what is not. The longer the halt is to be the more complete must be the observation and covering of all points of approach. As a rule, therefore, when the halt is long, the vanguard becomes always more and more extended into a line of posts. Whether the change becomes complete, or whether the idea of a concentrated Corps shall continue uppermost, depends chiefly on two circumstances. The first is the proximity of the contending Armies, the second is the nature of the country.
If the Armies are very close in comparison to the width of their front, then it will often be impossible to post a vanguard between them, and the Armies are obliged to place their dependence on a chain of outposts.
A concentrated Corps, as it covers the approaches to the Army less directly, generally requires more time and space to act efficiently; and therefore, if the Army covers a great extent of front, as in cantonments, and a Corps standing in mass is to cover all the avenues of approach, it is necessary that it should be at a considerable distance from the enemy; on this account winter quarters, for instance, are generally covered by a cordon of posts.
The second circumstance is the nature of the country; where, for example, any formidable obstacle of ground affords the means of forming a strong line of posts with but few troops, we should not neglect to take advantage of it.
Lastly, in winter quarters, the rigour of the season may also be a reason for breaking up the advance guard into a line of posts, because it is easier to find shelter for it in that way.
The use of a reinforced line of outposts was brought to great perfection by the Anglo-Dutch Army, during the campaign of 1794 and 1795, in the Netherlands, when the line of defence was formed by Brigades composed of all arms, in single posts, and supported by a reserve. Scharnhorst, who was with that Army, introduced this system into the Prussian Army on the Passarge in 1807. Elsewhere in modern times, it has been little adopted, chiefly because the Wars have been too rich in movement. But even when there has been occasion for its use it has been neglected, as for instance, by Murat, at Tarutino. A wider extension of his defensive line would have spared him the loss of thirty pieces of artillery in a combat of outposts.
It cannot be disputed that in certain circumstances, great advantages may be derived from this system. We propose to return to the subject on another occasion.
Note.—The importance of this chapter lies in this that it reveals the fact that Clausewitz had never clearly grasped the essential feature of Napoleon’s strategic method. Napoleon used his strong “Avant garde générale” not merely for observation and to delay the enemy, but by a vigorous offensive to “fix” him by paralysing his independent will power. Whilst he thus held his enemy’s attention the remainder of his army manœuvred to deliver the great decisive blow. Jena, Friedland, Lútzen are the chief examples. Of this method he left no distinct description in his later strategical writings, neither does it appear that his Marshals ever really grasped his idea. It has only been during the last fifteen years that it has been rediscovered by the careful investigations of the French General Staff. Moltke seems never to have understood its importance, hence the numerous critical situations that arose in August 1870, notably at Vionville. (See Bonnal’s “Manœuvre de St. Prival,” and Foch’s “Manœuvre pour a bataille.”—Ed.
[* ]And were beaten accordingly at the Katzbach, Gross Beeren. Dennewitz, 1813.—Ed.