On the whole then, when men speak of the Napoleonic system they seem to include two groups of ideasone which comprises the conception of war made with the whole force of the nation; the other, a group which includes the Cromwellian idea of persistent effort, Frederick's preference for the offensive at almost any risk, and finally the idea of the enemy's armed forces as the main objective, which was also Cromwell's.
It is the combination of these by no means original or very distinct ideas that we are told has brought about so entire a change in the conduct of war that it has become altogether a different thing. It is unnecessary for our purpose to consider how far the facts seem to support such a conclusion, for in the inherent nature of things it must be radically unsound. Neither war nor anything else can change in its essentials. If it appears to do so, it is because we are still mistaking accidents for essentials, and this is exactly how it struck the acutest thinkers of Napoleonic times.
For a while it is true they were bewildered, but so soon as they had had time to clear their heads from the din of the struggle in which they had taken part, they began to see that the new phenomena were but accidents after all. They perceived that Napoleon's methods, which had taken the world by storm, had met with success in wars of a certain nature only, and that when he tried to extend those methods to other natures of war he had met with failure and even disaster. How was this to be explained? What theory, for instance, would cover Napoleon's successes in Germany and Italy, as well as his failures in Spain and Russia? If the whole conception of war had changed, how could you account for the success of England, who had not changed her methods? To us the answer to these questions is of living and infinite importance. Our standpoint remains still unchanged. Is there anything inherent in the conception of war that justifies that attitude in our case? Are we entitled to expect from it again the same success it met with in the past?
The first man to enunciate a theory which would explain the phenomena of the Napoleonic era and co-ordinate them with previous history was General Carl von Clausewitz, a man whose arduous service on the Staff and the actual work of higher instruction had taught the necessity of systematising the study of his profession. He was no mere professor, but a soldier bred in the severest school of war. The pupil and friend of Sharnhorst and Gneisenau, he had served on the Staff of Blücher in 1813, he had been Chief of the Staff to Wallmoden in his campaign against Davoust on the Lower Elbe, and also to the Third Prussian Army Corps in the campaign of 1815. Thereafter for more than ten years he was Director of the General Academy of War at Berlin, and died in 1831 as Chief of the Staff to Marshal Gneisenau. For the fifty years that followed his death his theories and system were, as he expected they would be, attacked from all sides. Yet to-day his work is more firmly established than ever as the necessary basis of all strategical thought, and above all in the "blood and iron" school of Germany.
The process by which he reached his famous theory can be followed in his classical work On War and the Notes regarding it which he left behind him. In accordance with the philosophic fashion of his time he began by trying to formulate an abstract idea of war. The definition he started with was that "War is an act of violence to compel our opponent to do our will." But that act of violence was not merely "the shock of armies," as Montecuccoli had defined it a century and a half before. If the abstract idea of war be followed to its logical conclusion, the act of violence must be performed with the whole of the means at our disposal and with the utmost exertion of our will. Consequently we get the conception of two armed nations flinging themselves one upon the other, and continuing the struggle with the utmost strength and energy they can command till one or other is no longer capable of resistance. This Clausewitz called "Absolute War." But his practical experience and ripe study of history told him at once that "Real War" was something radically different. It was true, as he said, that Napoleon's methods had approximated to the absolute and had given some colour to the use of the absolute idea as a working theory. "But shall we," he acutely asks, "rest satisfied with this idea and judge all wars by it however much they may differ from itshall we deduce from it all the requirements of theory? We must decide the point, for we can say nothing trustworthy about a war plan until we have made up our minds whether war should only be of this kind or whether it may be of another kind." He saw at once that a theory formed upon the abstract or absolute idea of war would not cover the ground, and therefore failed to give what was required for practical purposes. It would exclude almost the whole of war from Alexander's time to Napoleon's. And what guarantee was there that the next war would confirm to the Napoleonic type and accommodate itself to the abstract theory? "This theory," he says, "is still quite powerless against the force of circumstances." And so it proved, for the wars of the middle nineteenth century did in fact revert to the pre-Napoleonic type.
In short, Clausewitz's difficulty in adopting his abstract theory as a working rule was that his practical mind could not forget that war had not begun with the Revolutionary era, nor was it likely to end with it. If that era had changed the conduct of war, it must be presumed that war would change again with other times and other conditions. A theory of war which did not allow for this and did not cover all that had gone before was no theory at all. If a theory of war was to be of any use as a practical guide it must cover and explain not only the extreme manifestation of hostility which he himself had witnessed, but every manifestation that had occurred in the past or was likely to recur in the future.
It was in casting about for the underlying causes of the oscillations manifested in the energy and intensity of hostile relations that he found his solution. His experience on the Staff, and his study of the inner springs of war, told him it was never in fact a question of purely military endeavour aiming always at the extreme of what was possible or expedient from a purely military point of view. The energy exhibited would always be modified by political considerations and by the depth of the national interest in the object of the war. He saw that real war was in fact an international relation which differed from other international relations only in the method we adopted to achieve the object of our policy. So it was he arrived at his famous theory"that war is a mere continuation of policy by other means."
At first sight there seems little enough in it. It may seem perhaps that we have been watching a mountain in labour and nothing but a mouse has been produced. But it is only upon some such simple, even obvious, formula that any scientific system can be constructed with safety. We have only to develop the meaning of this one to see how important and practical are the guiding lines which flow from it.
With the conception of war as a continuation of political intercourse before us, it is clear that everything which lies outside the political conception, everything, that is, which is strictly peculiar to military and naval operations, relates merely to the means which we use to achieve our policy. Consequently, the first desideratum of a war plan is that the means adopted must conflict as little as possible with the political conditions from which the war springs. In practice, of course, as in all human relations, there will be a compromise between the means and the end, between the political and the military exigencies. But Clausewitz held that policy must always be the master. The officer charged with the conduct of the war may of course demand that the tendencies and views of policy shall not be incompatible with the military means which are placed at his disposal; but however strongly this demand may react on policy in particular cases, military action must still be regarded only as a manifestation of policy. It must never supersede policy. The policy is always the object; war is only the means by which we obtain the object, and the means must always keep the end in view.