NOTE: This version of Clausewitz's On War is the long-obsolete J.J. Graham translation published in London in 1873. The 1976/84 Howard/Paret version is the  standard translation today.


Chapter XXVII

Defence of a Theatre of War

HAVING treated of the most important defensive means, we might perhaps be contented to leave the manner in which these means attach themselves to the plan of defence as a whole to be discussed in the last Book, which will be devoted to the Plan of a War; for from this every secondary scheme, either of attack or defence, emanates and is determined in its leading features; and moreover in many cases the plan of the war itself is nothing more than the plan of the attack or defence of the principal theatre of war. But we have not been able to commence with war as a whole, although in war more than in any other phase of human activity, the parts are shaped by the whole, imbued with and essentially altered by its character; instead of that, we have been obliged to make ourselves thoroughly acquainted, in the first instance, with each single subject as a separate part. Without this progress from the simple to the complex, a number of undefined ideas would have overpowered us, and the manifold phases of reciprocal action in particular would have constantly confused our conceptions. We shall therefore still continue to advance towards the whole by one step at a time; that is, we shall consider the defence of a theatre in itself, and look for the thread by which the subjects already treated of connect themselves with it.

The defensive, according to our conception, is nothing but the stronger form of combat. The preservation of our own forces and the destruction of those of the enemy—in a word, the victory—is the aim of this contest, but at the same time not its ultimate object.

That object is the preservation of our own political state and the subjugation of that of the enemy; or again, in one word, the desired peace, because it is only by it that this conflict adjusts itself, and ends in a common result.

But what is the enemy's state in connection with war? Above all things its military force is important, then its territory; but certainly there are also still many other things which, through particular circumstances, may obtain a predominant importance; to these belong, before all, foreign and domestic political relations, which sometimes decide more than all the rest. But although the military force and the territory of the enemy alone are still not the state itself, nor are they the only connections which the state may have with the war, still these two things are always preponderating, mostly immeasurably surpassing all other connections in importance. Military force is to protect the territory of the state, or to conquer that of an enemy; the territory on the other hand, constantly nourishes and renovates the military force. The two, therefore, depend on each other, mutually support each other, are equal in importance one to the other. But still there is a difference in their mutual relations. If the military force is destroyed, that is completely defeated, rendered incapable of further resistance, then the loss of the territory follows of itself; but on the other hand, the destruction of the military force by no means follows from the conquest of the country, because that force may of its own accord evacuate the territory, in order afterwards to reconquer it the more easily. Indeed, not only does the complete destruction of its army decide the fate of a country, but even every considerable weakening of its military force leads regularly to a loss of territory; on the other hand, every considerable loss of territory does not cause a proportionate diminution of military power; in the long run it will do so, but not always within the space of time in which a war is brought to a close.

From this it follows that the preservation of our own military power, and the diminution or destruction of that of the enemy, take precedence in importance over the occupation of territory, and, therefore, is the first object which a general should strive for. The possession of territory only presses for consideration as an object if that means (diminution or destruction of the enemy's military force) has not effected it.

If the whole of the enemy's military power was united in one army, and if the whole war consisted of one battle, then the possession of the country would depend on the issue of that battle; destruction of the enemy's military forces, conquest of his country and security of our own, would follow from that result, and, in a certain measure, be identical with it. Now the question is, what can induce the defensive to deviate from this simplest form of the act of warfare, and distribute his power in space? The answer is, the insufficiency of the victory which he might gain with all his forces united. Every victory has its sphere of influence. If this extends over the whole of the enemy's state, consequently over the whole of his military force and his territory, that is, if all the parts are carried along in the same movement, which we have impressed upon the core of his power, then such a victory is all that we require, and a division of our forces would not be justified by sufficient grounds. But if there are portions of the enemy's military force, and of country belonging to either party, over which our victory would have no effect, then we must give particular attention to those parts; and as we cannot unite territory like a military force in one point, therefore we must divide our forces for the purpose of attacking or defending those portions.

It is only in small, compactly shaped states that it is possible to have such a unity of military force, and that probably all depends upon a victory over that force. Such a unity is practically impossible when larger tracts of country, having for a great extent boundaries conterminious with our own, are concerned, or in the case of an alliance of several surrounding states against us. In such cases, divisions of force must necessarily take place, giving occasion to different theatres of war.

The effect of a victory will naturally depend on its greatness, and that on the mass of the conquered troops. Therefore the blow which, if successful, will produce the greatest effect, must be made against that part of the country where the greatest number of the enemy's forces are collected together; and the greater the mass of our own forces which we use for this blow, so much the surer shall we be of this success. This natural sequence of ideas leads us to an illustration by which we shall see this truth more clearly; it is the nature and effect of the centre of gravity in mechanics.

As the centre of gravity is always situated where the greatest mass of matter is collected, and as a shock against the centre of gravity of a body always produces the greatest effect, and further, as the most effective blow is struck with the centre of gravity of the power used, so it is also in war. The armed forces of every belligerent, whether of a single state or of an alliance of states, have a certain unity, and in that way, connection; but where connection is there come in analogies of the centre of gravity. There are, therefore, in these armed forces certain centres of gravity, the movement and direction of which decide upon other points, and these centres of gravity are situated where the greatest bodies of troops are assembled. But just as, in the world of inert matter, the action against the centre of gravity has its measure and limits in the connection of the parts, so it is in war, and here as well as there the force exerted may easily be greater than the resistance requires, and then there is a blow in the air, a waste of force.

What a difference there is between the solidity of an army under one standard, led into battle under the personal command of one general, and that of an allied army extended over 50 or 100 miles, or it may be even based upon quite different sides (of the theatre of war). There we see coherence in the strongest degree, unity most complete; here unity in a very remote degree often only existing in the political view held in common, and in that also in a miserable and insufficient degree, the cohesion of parts mostly very weak, often quite an illusion.

Therefore, if on the one hand, the violence with which we wish to strike the blow prescribes the greatest concentration of force, so in like manner, on the other hand, we have to fear every undue excess as a real evil, because it entails a waste of power, and that in turn a deficiency of power at other points.

To distinguish these "centra gravitatis" in the enemy's military power, to discern their spheres of action is, therefore, a supreme act of strategic judgment. We must constantly ask ourselves, what effect the advance or retreat of part of the forces on either side will produce on the rest.

We do not by this lay claim in any way to the discovery of a new method, we have only sought to explain the foundation of the method of all generals, in every age, in a manner which may place its connection with the nature of things in a clearer light.

How this conception of the centre of gravity of the enemy's force affects the whole plan of the war, we shall consider in the last book, for that is the proper place for the subject, and we have only borrowed it from there to avoid leaving any break in the sequence of ideas. By the introduction of this view we have seen the motives which occasion a partition of forces in general. These consist fundamentally of two interests which are in opposition to each other; the one, the possession of territory strives to divide the forces; the other, the effort of force against the centre of gravity of the enemy's military power, combines them again up to a certain point.

Thus it is that theatres of war or particular army regions originate. These are those boundaries of the area of the country and of the forces thereon distributed, within which every decision given by the principal force of such a region extends itself directly over the whole, and carries on the whole with it in its own direction. We say directly, because a decision on one theatre of war must naturally have also an influence more or less over those adjoining it.

Although it lies quite in the nature of the thing, we must again remind our readers expressly that here as well as everywhere else our definitions are only directed at the centres of certain speculative regions, the limits of which we neither desire to, nor can we, define by sharp lines.

We think, therefore, a theatre of war, whether large or small, with its military force, whatever may be the size of that, represents a unity which maybe reduced to one centre of gravity. At this centre of gravity the decision must take place, and to be conqueror here means to defend the theatre of war in the widest sense.