On War

by Carl von Clausewitz

The different steps in the defence which we have become acquainted with in the chapter on the methods of defence, are completely homogeneous with these fundamental conditions; there will therefore be no difficulty in connecting them with the same, according to the special requirements of each case. But there is one point which seems at first sight to involve a contradiction in itself, and which, as one of the most important in the defence, requires explanation so much the more. It is the hitting upon the exact centre of gravity of the enemy’s force.

If the defender ascertains in time the roads by which the enemy will advance, and upon which in particular the great mass of his force will be found for a certainty, he may march against him on that road. This will be the most usual case, for although the defence precedes the attack in measures of a general nature, in the establishment of strong places, great arsenals, and depôts, and in the peace establishment of his army, and thus gives a line of direction to the assailant in his preparations, still, when the campaign really opens, the defender, in relation to the aggressor, has the peculiar advantage in general of playing the last hand.

To attack a foreign country with a large army, very considerable preparations are required. Provisions, stores, and articles of equipment of all kinds must be collected, which is a work of time. While these preparations are going on, the defender has time to prepare accordingly, in regard to which we must not forget that the defensive requires less time, generally speaking, because in every state things are prepared rather for the defensive than the offensive.

But although this may hold good in the majority of cases, there is always a possibility that, in particular cases, the defensive may remain in uncertainty as to the principal line by which the enemy intends to advance; and this case is more likely to occur when the defence is dependent on measures which of themselves take a good deal of time, as for example, the preparation of a strong position. Further, supposing the defender places himself on the line by which the aggressor is advancing, then, unless the defender is prepared to take the initiative by attacking the aggressor, the latter may avoid the position which the defender has taken up, by only altering a little his line of advance, for in the cultivated parts of Europe we can never be so situated that there are not roads to the right or left by which any position may be avoided. Plainly, in such a case the defender could not wait for his enemy in a position, or at least could not wait there in the expectation of giving battle.

But before entering on the means available to the defensive in this case, we must inquire more particularly into the nature of such a case, and the probability of its occurrence.

Naturally there are in every State, and also in every theatre of war (of which alone we are at present speaking), objects and points upon which an attack is likely to be more efficacious than anywhere else. Upon this we think it will be better to speak when we come to the attack. Here we shall confine ourselves to observing that, if the most advantageous object and point of attack is the motive for the assailant in the direction of his blow, this motive reacts on the defensive, and must be his guide in cases in which he knows nothing of the intentions of his adversary. If the assailant does not take this direction which is favourable to him, he foregoes part of his natural advantages. It is evident that, if the defender has taken up a position in that direction, the evading his position, or passing round, is not to be done for nothing; it costs a sacrifice. From this it follows that there is not on the side of the defender such a risk of missing the direction of his enemy; neither on the other hand, is it so easy for the assailant to pass round his adversary as appears at first sight, because there exists beforehand a very distinct, and in most cases preponderating, motive in favour of one or the other direction, and that consequently the defender, although his preparations are fixed to one spot, will not fail in most cases to come in contact with the mass of the enemy’s forces. In other words, if the defender has put himself in the right position, he may be almost sure that the assailant will come to meet him.

But by this we shall not and cannot deny the possibility of the defender sometimes not meeting with the assailant after all these arrangements, and therefore the question arises, what he should then do, and how much of the real advantages of his position still remain available to him.

If we ask ourselves what means still remain generally to the defender when the assailant passes by his position, they are the following:—

1. To divide his forces instantly, so as to be certain to find the assailant with one portion, and then to support that portion with the other.

2. To take up a position with his force united, and in case the assailant passes by him, to push on rapidly in front of him by a lateral movement. In most cases there will not be time to make such a movement directly to a flank, it will therefore be necessary to take up the new position somewhat further back.