On War

by Carl von Clausewitz

If we suppose an army with its theatre of war intended for defence, the defence may be made as follows:

1. By attacking the enemy the moment he enters the theatre of war. (Mollwitz, Hohenfriedberg).

2. By taking up a position close on the frontier, and waiting till the enemy appears with the intention of attacking it, in order then to attack him (Czaslau, Soor, Rosbach). Plainly this second mode of proceeding, partakes more of endurance, we “wait for” longer; and although the time gained by it as compared with that gained in the first, may be very little, or none at all if the enemy’s attack actually takes place, still, the battle which in the first case was certain, is in the second much less certain, perhaps the enemy may not be able to make up his mind to attack; the advantage of the “waiting for,” is then at once greater.

3. By the army in such position not only awaiting the decision of the enemy to fight a battle, that is his appearance in front of the position, but also waiting to be actually assaulted (in order to keep to the same general, Bunzelwitz). In such case, we fight a regular defensive battle, which however, as we have before said, may include offensive movements with one or more parts of the army. Here also, as before, the gain of time does not come into consideration, but the determination of the enemy is put to a new proof; many a one has advanced to the attack, and at the last moment, or after one attempt given it up, finding the position of the enemy too strong.

4. By the army transferring its defence to the heart of the country. The object of retreating into the interior is to cause a diminution in the enemy’s strength, and to wait until its effects are such that his forward march is of itself discontinued, or at least until the resistance which we can offer him at the end of his career is such as he can no longer overcome.

This case is exhibited in the simplest and plainest manner, when the defensive can leave one or more of his fortresses behind him, which the offensive is obliged to besiege or blockade. It is clear in itself, how much his forces must be weakened in this way, and what a chance there is of an opportunity for the defensive to attack at some point with superior forces.

But even when there are no fortresses, a retreat into the interior of the country may procure by degrees for the defender that necessary equilibrium or that superiority which was wanting to him on the frontier; for every forward movement in the strategic attack lessens its force, partly absolutely, partly through the separation of forces which becomes necessary, of which we shall say more under the head of the “Attack.” We anticipate this truth here as we consider it as a fact sufficiently exemplified in all wars.

Now in this fourth case the gain of time is to be looked upon as the principal point of all. If the assailant lays siege to our fortresses, we have time till their probable fall, (which may be some weeks or in some cases months); but if the weakening, that is the expenditure, of the force of the attack is caused by the advance, and the garrisoning or occupation of certain points, therefore merely through the length of the assailant’s march, then the time gained in most cases becomes greater, and our action is not so much restricted in point of time.

Besides the altered relations between offensive and defensive in regard to power which is brought about at the end of this march, we must bring into account in favour of the defensive an increased amount of the advantage of the state of “waiting for.” Although the assailant by this advance may not in reality be weakened to such a degree that he is unfit to attack our main body where he halts, still he will probably want resolution to do so, for that is an act requiring more resolution in the position in which he is now placed, than would have sufficed when operations had not extended beyond the frontier: partly, because the powers are weakened, and no longer in fresh vigour, while the danger is increased; partly, because with an irresolute commander the possession of that portion of the country which has been obtained is often sufficient to do away with all idea of a battle, because he either really believes or assumes as a pretext, that it is no longer necessary. By the offensive thus declining to attack, the defensive certainly does not acquire, as he would on the frontier, a sufficient result of a negative kind, but still there is a great gain of time.

It is plain that, in all the four methods indicated, the defensive has the benefit of the ground or country, and likewise that he can by that means bring into cooperation his fortresses and the people; moreover these efficient principles increase at each fresh stage of the defence, for they are a chief means of bringing about the weakening of the enemy’s force in the fourth stage. Now as the advantages of the “state of expectation” increase in the same direction, therefore it follows of itself that these stages are to be regarded as a real intensifying of the defence, and that this form of war always gains in strength the more it differs from the offensive. We are not afraid on this account of any one accusing us of holding the opinion that the most passive defence would therefore be the best. The action of resistance is not weakened at each new stage, it is only delayed, postponed. But the assertion that a stouter resistance can be offered in a strong judiciously entrenched position, and also that when the enemy has exhausted his strength in fruitless efforts against such a position a more effective counterstroke may be levelled at him, is surely not unreasonable. Without the advantage of position Daun would not have gained the victory at Kollin, and as Frederick the Great only brought off 18,000 men from the field of battle, if Daun had pursued him with more energy the victory might have been one of the most brilliant in military history.