On War

by Carl von Clausewitz

If from this extreme we take the opposite direction, we find that the smaller the mass of troops in one column the greater the ease and precision with which the march can be performed. The result of this is the need of a division quite irrespective of that division of an army in separate parts which belongs to its position; therefore, although the division into columns of march originates in the strategic disposition in general, it does not do so in every particular case. A great mass which is to be concentrated at any one point must necessarily be divided for the march. But even if a disposition of the army in separate parts causes a march in separate divisions, sometimes the conditions of the primitive disposition, sometimes those of the march, are paramount. For instance, if the disposition of the troops is one made merely for rest, one in which a battle is not expected, then the conditions of the march predominate, and these conditions are chiefly the choice of good, well-frequented roads. Keeping in view this difference, we choose a road in the one case on account of the quarters and camping ground, in the other we take the quarters and camps such as they are, on account of the road. When a battle is expected, and everything depends on our reaching a particular point with a mass of troops, then we should think nothing of getting to that point by even the worst by-roads, if necessary; if, on the other hand, we are still on the journey to the theatre of war, then the nearest great roads are selected for the columns, and we look out for the best quarters and camps that can be got near them.

Whether the march is of the one kind or the other, if there is a possibility of a combat, that is within the whole region of actual war, it is an invariable rule in the modern art of war to organise the columns so that the mass of troops composing each column is fit of itself to engage in an independent combat. This condition is satisfied by the combination of the three arms, by an organised subdivision of the whole, and by the appointment of a competent commander. Marches, therefore, have been the chief cause of the new order of battle, and they profit most by it.

When in the middle of the last century, especially in the theatre of war in which Frederick II. was engaged, generals began to look upon movement as a principle belonging to fighting, and to think of gaining the victory by the effect of unexpected movements, the want of an organised order of battle caused the most complicated and laborious evolutions on a march. In carrying out a movement near the enemy, an army ought to be always ready to fight; but at that time they were never ready to fight unless the whole army was collectively present, because nothing less than the army constituted a complete whole. In a march to a flank, the second line, in order to be always at the regulated distance, that is about a quarter of a mile from the first, had to march up hill and down dale, which demanded immense exertion, as well as a great stock of local knowledge; for where can one find two good roads running parallel at a distance of a quarter of a mile from each other? The cavalry on the wings had to encounter the same difficulties when the march was direct to the front. There was other difficulty with the artillery, which required a road for itself, protected by infantry; for the lines of infantry required to be continuous lines, and the artillery increased the length of their already long trailing columns still more, and threw all their regulated distances into disorder. It is only necessary to read the dispositions for marches in Tempelhof’s History of the Seven Years’ War, to be satisfied of all these incidents and of the restraints thus imposed on the action of war.

But since then the modern art of war has subdivided armies on a regular principle, so that each of the principal parts forms in itself a complete whole, of small proportions, but capable of acting in battle precisely like the great whole, except in one respect, which is, that the duration of its action must be shorter. The consequence of this change is, that even when it is intended that the whole force should take part in a battle, it is no longer necessary to have the columns so close to each other that they may unite before the commencement of the combat; it is sufficient now if the concentration takes place in the course of the action.

The smaller a body of troops the more easily it can be moved, and therefore the less it requires that subdivision which is not a result of the separate disposition, but of the unwieldiness of the mass. A small body, therefore, can march upon one road, and if it is to advance on several lines it easily finds roads near each other which are as good as it requires. The greater the mass the greater becomes the necessity for subdividing, the greater becomes the number of columns, and the want of made roads, or even great high roads, consequently also the distance of the columns from each other. Now the danger of this subdivision is arithmetically expressed in an inverse ratio to the necessity for it. The smaller the parts are, the more readily must they be able to render assistance to each other; the larger they are, the longer they can be left to depend on themselves. If we only call to mind what has been said in the preceding book on this subject, and also consider that in cultivated countries at a few miles distance from the main road there are always other tolerably good roads running in a parallel direction, it is easy to see that, in regulating a march, there are no great difficulties which make rapidity and precision in the advance incompatible with the proper concentration of force. In a mountainous country parallel roads are both scarce, and the difficulties of communication between them great; but the defensive powers of a single column are very much greater.

In order to make this idea clearer let us look at it for a moment in a concrete form.

A division of 8,000 men, with its artillery and other carriages, takes up, as we know by experience in ordinary cases, a space of one league; if, therefore, two divisions march one after the other on the same road, the second arrives one hour after the first; but now, as said in the sixth chapter of the fourth book, a division of this strength is quite capable of maintaining a combat for several hours, even against a superior force, and, therefore, supposing the worst, that is, supposing the first had to commence a fight instantaneously, still the second division would not arrive too late. Further, within a league right and left of the road on which we march, in the cultivated countries of central Europe there are, generally, lateral roads which can be used for a march, so that there is no necessity to go across country, as was so often done in the Seven Years’ War.

Again, it is known by experience that the head of a column composed of four divisions and a reserve of cavalry, even on indifferent roads, generally gets over a march of three miles in eight hours; now, if we reckon for each division one league in depth, and the same for the reserve cavalry and artillery, then the whole march will last thirteen hours. This is no great length of time, and yet in this case forty thousand men would have marched over the same road. But with such a mass as this we can make use of lateral roads, which are to be found at a greater distance, and therefore easily shorten the march. If the mass of troops marching on the same road is still greater than above supposed, then it is a case in which the arrival of the whole on the same day is no longer indispensable, for such masses never give battle now the moment they meet, usually not until the next day.

We have introduced these concrete cases, not as exhausting considerations of this kind, but to make ourselves more intelligible, and by means of this glance at the results of experience to show that in the present mode of conducting war the organisation of marches no longer offers such great difficulties; that the most rapid marches, executed with the greatest precision, no longer require either that peculiar skill or that exact knowledge of the country which was needed for Frederick’s rapid and exact marches in the Seven Years’ War. Through the existing organisation of armies, they rather go on now almost of themselves, at least without any great preparatory plans. In times past, battles were conducted by mere word of command, but marches required a regular plan, now the order of battle requires the latter, and for a march the word of command almost suffices.

As is well known, all marches are either perpendicular [to the front] or parallel. The latter, also called flank marches, alter the geometrical position of the divisions; those parts which, in position, were in line, will follow one another, and vice versa. Now, although the line of march may be at any angle with the front, still the order of the march must decidedly be of one or other of these classes.