If we have here traced the position before a fortress to reasons of a superior and absolute order, and defended its adoption on those grounds, we have still to observe that there is a motive of a secondary class which, though a more obvious one, is not sufficient of itself alone, not being absolute; we refer to the use which is made by armies of the nearest fortress as a depôt of provisions and munitions of war. This is so convenient, and presents so many advantages, that a general will not easily make up his mind to draw his supplies of all kinds from more distant places, or to lodge them in open towns. But if a fortress is the great magazine of an army, then the position before it is frequently a matter of absolute necessity, and in most cases is very natural. But it is easy to see that this obvious motive, which is easily over-valued by those who are not in the habit of looking far before them, is neither sufficient to explain all cases, nor are the circumstances connected with it of sufficient importance to entitle it to give a final decision.
The capture of one or more fortresses without risking a battle, is such a very natural object of all attacks which do not aim at a decision on the field of battle, that the defender makes it his principal business to thwart this design. Thus it is that on theatres of war, containing a number of fortresses, we find these places made the pivots of almost all the movements; we find the assailant seeking to approach one of them unexpectedly, and employing various feints to aid his purpose, and the defender immediately seeking to stop him by well-prepared movements. Such is the general character of almost all the campaigns of Louis XIV. in the Netherlands up to the time of Marshal Saxe.
So much for the covering of fortresses.