The course of improvement in tactics since the Middle Ages, with the ever increasing strength of armies, likewise contributed to bring mountainous districts in this sense more within the scope of military action.
The chief characteristic of mountain defence is its complete passivity; in this light the tendency towards the defence of mountains was very natural before armies attained to their present capability of movement. But armies were constantly becoming greater, and on account of the effect of fire-arms began to extend more and more into long thin lines connected with a great deal of art, and on that account very difficult, often almost impossible, to move. To dispose, in order of battle, such an artistic machine, was often half a day’s work, and half the battle; and almost all which is now attended to in the preliminary plan of the battle was included in this first disposition or drawing up. After this work was done it was therefore difficult to make any modifications to suit new circumstances which might spring up; from this it followed that the assailant, being the last to form his line of battle, naturally adapted it to the order of battle adopted by the enemy, without the latter being able in turn to modify his in accordance. The attack thus acquired a general superiority, and the defensive had no other means of reinstating the balance than that of seeking protection from the impediments of ground, and for this nothing was so favourable in general as mountainous ground. Thus it became an object to couple, as it were, the army with a formidable obstacle of ground, and the two united then made common cause. The battalion defended the mountain, and the mountain the battalion; so the passive defence through the aid of mountainous ground became highly efficacious, and there was no other evil in the thing itself except that it entailed a greater loss of freedom of movement, but of that quality they did not understand the particular use at that time.
When two antagonistic systems act upon each other, the exposed, that is, the weak point on the one side always draws upon itself the blows from