On War

by Carl von Clausewitz

are the principal circumstances under which the lines of communication of an army may be interrupted by a relatively small proportion of armed forces on the side of the enemy; in order to make this interruption effectual, a fourth condition is still requisite, which is a certain duration of time. Respecting this point, we beg attention to what has been said in the fifteenth chapter of the fifth book.

But these four conditions are only the chief points which relate to the subject; a number of local and special circumstances attach themselves to these, and often attain to an influence more decisive and important than that of the principal ones themselves. Selecting only the most essential, we mention the state of the roads, the nature of the country through which they pass, the means of cover which are afforded by rivers, mountains, and morasses, the seasons and weather, the importance of particular convoys, such as siege trains, the number of light troops, etc., etc.

On all these circumstances, therefore, will depend the effect with which a general can act on his opponent’s communications; and by comparing the result of the whole of these circumstances on the one side with the result of the whole on the other, we obtain a just estimate of the relative advantages of both systems of communication, on which will depend which of the two generals can play the highest game.

What here seems so prolix in the explanation is often decided in the concrete case at first sight; but still, the tact of a practised judgment is required for that, and person must have thought over every one of the cases now developed in order to see in its true light the absurdity of those critical writers who think they have settled something by the mere words “turning” and “acting on a flank,” without giving their reasons.

We now come to the second chief condition, under which the strategic action against the enemy’s flank may take place.

If the enemy is hindered from advancing by any other cause but the resistance which our army opposes, let that cause be what it may, then our army has no reason to be apprehensive about weakening itself by sending out detachments to harass the enemy; for if the enemy should attempt to chastise us by an attack, we have only to yield some ground and decline the combat. This is what was done by the chief Russian army at Moscow in 1812. But it is not at all necessary that everything should be again on the same great scale as in that campaign for such a case to happen again. In the first Silesian war, Frederick the Great was each time in this situation, on the frontiers of Bohemia and Moravia, and in the complex affairs relating to generals and their armies, many causes of different kinds, particularly political ones, may be imagined, which make further advance an impossibility.

As in the case now supposed more forces may be spared to act against the enemy’s flank, the other conditions need not be quite so favourable: even the nature of our communications in relation to those of the enemy need not give us the advantage in that respect, as an enemy who is not in a condition to make any particular use of our further retreat is not likely to use his right to retaliate, but will rather be anxious about the direct covering of his own line of retreat.

Such a situation is therefore very well suited to obtain for us, by means less brilliant and complete but less dangerous than a victory, those results which it would be too great a risk to seek to obtain by a battle.

As in such a case we feel little anxiety about exposing our own line of communications, by taking up a position on one or other flank, and as the enemy by that means may always be comspelled to form front obliquely to his line of communications, therefore this one of the conditions above named will seldom fail to occur. The more the rest of the conditions, as well as other circumstances, co-operate, so much the more certain are we of success from the means now in question; but the fewer favourable circumstances exist, the more will all depend on superior skill in combination, and promptitude and precision in the execution.

Here is the proper field for strategic manœuvres, such as are to be found so frequently in the Seven Years’ War, in Silesia and Saxony, and in the campaigns of 1760 and 1762. If, in many wars in which only a moderate amount of elementary force is displayed, such strategic manœuvring very often appears, this is not because the commander on each occasion found himself at the end of his career, but because want of resolution and courage, and of an enterprising spirit, and dread of responsibility, have often supplied the place of real impediments; for a case in point, we have only to call to mind Field Marshal Daun.