On War

by Carl von Clausewitz

Every assailant in advancing diminishes his military strength by the advance; we shall consider this more in detail in the seventh book; here we must assume that result which we may the more readily do as it is clearly shown by military history in every campaign in which there has been a considerable advance.

This loss in the advance is increased if the enemy has not been beaten, but withdraws of his own accord with his forces intact, and offering a steady continuous resistance, sells every step of ground at a bloody price, so that the advance is a continuous combat for ground and not a mere pursuit.

On the other hand, the losses which a party on the defensive suffers on a retreat, are much greater if his retreat has been preceded by a defeat in battle than if his retreat is voluntary. For if he is able to offer the pursuer the daily resistance which we expect on a voluntary retreat, his losses would be at least the same in that way, over and above which those sustained in the battle have still to be added. But how contrary to the nature of the thing such a supposition as this would be! The best army in the world if obliged to retire far into the country after the loss of a battle, will suffer losses on the retreat, beyond measure out of proportion; and if the enemy is considerably superior, as we suppose him, in the case of which we are now speaking, if he pursues with great energy as has almost always been done in modern wars, then there is the highest probability that a regular flight takes place by which the army is usually completely ruined.

A regularly measured daily resistance, that is, one which each time only lasts as long as the balance of success in the combat can be kept wavering, and in which we secure ourselves from defeat by giving up the ground which has been contested at the right moment, will cost the assailant at least as many men as the defender in these combats, for the loss which the latter by retiring now and again must unavoidably suffer in prisoners, will be balanced by the losses of the other under fire, as the assailant must always fight against the advantages of the ground. It is true that the retreating side loses entirely all those men who are badly wounded, but the assailant likewise loses all his in the same case for the present, as they usually remain several months in the hospitals.

The result will be that the two armies will wear each other away in nearly equal proportions in these perpetual collisions.

It is quite different in the pursuit of a beaten army. Here the troops lost in battle, the general disorganisation, the broken courage, the anxiety about the retreat, make such a resistance on the part of the retreating army very difficult, in many cases impossible; and the pursuer who, in the former case, advances extremely cautiously, even hesitatingly, like a blind man, always groping about, presses forward in the latter case with the firm tread of the conqueror, with the overweening spirit which good fortune imparts, with the confidence of a demigod, and the more daringly he urges the pursuit so much the more he hastens on things in the direction which they have already taken, because here is the true field for the moral forces which intensify and multiply themselves without being restricted to the rigid numbers and measures of the physical world.

It is therefore very plain how different will be the relations of two armies according as it is by the first or the second of the above ways, that they arrive at that point which may be regarded as the end of the assailant’s course.

This is merely the result of the mutual destruction; to this must now be added the reductions which the advancing party suffers otherwise in addition, and respecting which, as already said, we refer to the seventh book; further, on the other hand, we have to take into account reinforcements which the retreating party receives in the great majority of cases, by forces subsequently joining him either in the form of help from abroad or through persistent efforts at home.

Lastly, there is, in the means of subsistence, such a disproportion between the retreating side and the advancing, that the first not uncommonly lives in superfluity when the other is reduced to want.

The army in retreat has the means of collecting provisions everywhere, and he marches towards them, whilst the pursuer must have everything brought after him, which, as long as he is in motion, even with the shortest lines of communication, is difficult, and on that account begets scarcity from the very first.