In mountains every movement is slower and more difficult, costs also more time, and more men as well, if within the sphere of danger. But the loss of the assailant in time and men is the standard by which the defensive resistance is measured. As long as the movement is all on the side of the offensive so long the defensive has a marked advantage; but as soon as the defensive resorts to this principle of movement also, that advantage ceases. Now from the nature of the thing, that is to say, on tactical grounds, a relative resistance allows of a much greater degree of passivity than one which is intended to lead to a decisive result, and it allows this passivity to be carried to an extreme, that is, to the end of the combat, which in the other case can never happen. The impeding element of mountain ground, which as a medium of greater density weakens all positive activity, is, therefore, completely suited to the passive defence.
We have already said that a small post acquires an extraordinary strength by the nature of the ground; but although this tactical result in general requires no further proof, we must add to what we have said some explanation. We must be careful here to draw a distinction between what is relatively and what is absolutely small. If a body of troops, let its size be what it may, isolates a portion of itself in a position, this portion may possibly be exposed to the attack of the whole body of the enemy’s troops, therefore of a superior force, in opposition to which it is itself small. There, as a rule, no absolute but only a relative defence can be the object. The smaller the post in relation to the whole body from which it is detached and in relation to the whole body of the enemy, the more this applies.
But a post also which is small in an absolute sense, that is, one which is not opposed by an enemy superior to itself, and which, therefore, may aspire to an absolute defence, a real victory, will be infinitely better off in mountains than a large army, and can derive more advantage from the ground as we shall show further on.