FIRST of all we must inquire into the circumstances which give the victory in a battle.
Of superiority of numbers, and bravery, discipline, or other qualities of an army, we say nothing here, because, as a rule, they depend on things which lie out of the province of the art of war in the sense in which we are now considering it; besides which they exercise the same effect in the offensive as the defensive; and, moreover also, the superiority in numbers in general cannot come under consideration here, as the number of troops is likewise a given quantity or condition, and does not depend on the will or pleasure of the general. Further, these things have no particular connection with attack and defence. But, irrespective of these things, there are other three which appear to us of decisive importance, these are: surprise, advantage of ground, and the attack from several quarters. The surprise produces an effect by opposing to the enemy a great many more troops than he expected at some particular point. The superiority in numbers in this case is very different to a general superiority of numbers; it is the most powerful agent in the art of war.—The way in which the advantage of ground contributes to the victory is intelligible enough of itself, and we have only one observation to make which is, that we do not confine our remarks to obstacles which obstruct the advance of an enemy, such as scarped grounds, high hills, marshy streams, hedges, inclosures, etc.; we also allude to the advantage which ground affords as cover, under which troops are concealed from view. Indeed we may say that even from ground which is quite unimportant a person acquainted with the locality may derive assistance. The attack from several quarters includes in itself all tactical turning movements great and small, and its effects are derived partly from the double execution obtained in this way from fire-arms, and partly from the enemy's dread of his retreat being cut off.
Now how do the offensive and defensive stand respectively in relation to these things?
Having in view the three principles of victory just described, the answer to this question is, that only a small portion of the first and last of these principles is in favour of the offensive, whilst the greater part of them, and the whole of the second principle, are at the command of the party acting defensively.
The offensive side can only have the advantage of one complete surprise of the whole mass with the whole, whilst the defensive is in a condition to surprise incessantly, throughout the whole course of the combat, by the force and form which he gives to his partial attacks.
The offensive has greater facilities than the defensive for surrounding and cutting off the whole, as the latter is in a manner in a fixed position while the former is in a state of movement having reference to that position. But the superior advantage for an enveloping movement, which the offensive possesses, as now stated, is again limited to a movement against the whole mass; for during the course of the combat, and with separate divisions of the force, it is easier for the defensive than for the offensive to make attacks from several quarters, because, as we have already said, the former is in a better situation to surprise by the force and form of his attacks.
That the defensive in an especial manner enjoys the assistance which ground affords is plain in itself; as to what concerns the advantage which the defensive has in surprising by the force and form of his attacks, that results from the offensive being obliged to approach by roads and paths where he may be easily observed, whilst the defensive conceals his position, and, until almost the decisive moment, remains invisible to his opponent.—Since the true method of defence has been adopted, reconnaissances have gone quite out of fashion, that is to say, they have become impossible. Certainly reconnaissances are still made at times, but they seldom bring home much with them. Immense as is the advantage of being able to examine well a position, and become perfectly acquainted with it before a battle, plain as it is that he (the defensive) who lies in wait near such a chosen position can much more easily effect a surprise than his adversary, yet still to this very hour the old notion is not exploded that a battle which is accepted is half lost. This comes from the old kind of defensive practised twenty years ago, and partly also in the Seven Years' War, when the only assistance expected from the ground was that it should be difficult of approach in front (by steep mountain slopes, etc., etc.), when the little depth of the positions and the difficulty of moving the flanks produced such weakness that the armies dodged one another from one hill to another, which increased the evil. If some kind of support were found on which to rest the wings, then all depended on preventing the army stretched along between these points, like a piece of work on an embroidery frame, from being broken through at any point. The ground occupied possessed a direct value at every point, and therefore a direct defence was required everywhere. Under such circumstances, the idea of making a movement or attempting a surprise during the battle could not be entertained; it was the exact reverse of what constitutes a good defence, and of that which the defence has actually become in modern warfare.
In reality, contempt for the defensive has always been the result of some particular method of defence having become worn out (outlived its period); and this was just the case with the method we have now mentioned, for in times antecedent to the period we refer to, that very method was superior to the offensive.
If we go through the progressive development of the modern art of war, we find that at the commencement—that is the Thirty Years' War and the war of the Spanish Succession—the deployment and drawing up of the army in array, was one of the great leading points connected with the battle. It was the most important part of the plan of the battle. This gave the defensive, as a rule, a great advantage, as he was already drawn up and deployed. As soon as the troops acquired greater capability of manœuvring, this advantage ceased, and the superiority passed over to the side of the offensive for a time. Then the defensive sought shelter behind rivers or deep valleys, or on high land. The defensive thus recovered the advantage, and continued to maintain it until the offensive acquired such increased mobility and expertness in manœuvring that he himself could venture into broken ground and attack in separate columns, and therefore became able to turn his adversary. This led to a gradual increase in the length of positions, in consequence of which, no doubt, it occurred to the offensive to concentrate at a few points, and break through the enemy's thin line. The offensive thus, for a third time, gained the ascendancy, and the defence was again obliged to alter its system. This it has done in recent wars by keeping its forces concentrated in large masses, the greater part not deployed, and, where possible, concealed, thus merely taking up a position in readiness to act according to the measures of the enemy as soon as they are sufficiently revealed.
This does not preclude a partially passive defence of the ground; its advantage is too great for it not to be used a hundred times in a campaign. But that kind of passive defence of the ground is usually no longer the principal affair: that is what we have to do with here.
If the offensive should discover some new and powerful element which it can bring to its assistance—an event not very probable, seeing the point of simplicity and natural order to which all is now brought—then the defence must again alter its method. But the defensive is always certain of the assistance of ground, which insures to it in general its natural superiority, as the special properties of country and ground exercise a greater influence than ever on actual warfare.