If we reflect on these four points in the whole of their effects, we see that an important fortress in a direct and in an indirect way certainly gives some security to a much greater extent of cantonments than we should think at first sight. “Some security” we say, for all these indirect agencies do not render the advance of the enemy impossible; they only make it more difficult, and a more serious consideration; consequently less probable and less of a danger for the defensive. But that is also all that was required, and all that should be understood in this case under the term covering. The real direct security must be attained by means of outposts and the arrangement of the cantonments themselves.
There is, therefore, some truth in ascribing to a great fortress the capability of covering a wide extent of cantonments lying in rear of it; but it is also not to be denied that often in plans of real campaigns, but still oftener in historical works, we meet with vague and empty expressions, or illusory views in connection with this subject. For if that covering is only realised by the co-operation of several circumstances, if it then also only produces a diminution of the danger, we can easily see that, in particular cases, through special circumstances, above all, through the boldness of the enemy, this whole covering may prove an illusion, and therefore in actual war we must not content ourselves with assuming hastily at once the efficacy of such and such a fortress, but carefully examine and study each single case on its own merits.
9. As covering a province not occupied. If during war province is either not occupied at all, or only occupied by an insufficient force, and likewise exposed more or less to incursions from flying columns, then a fortress, if not too unimportant in size, may be looked upon as a covering, or, if we prefer, as a security for this province. As a security it may at all events be regarded, for an enemy cannot become master of the province until he has taken it, and that gives us time to hasten to its defence. But the actual covering can certainly only be supposed very indirect, or as not preperly belonging to it. That is, the fortress by its active opposition can only in some measure check the incursions of hostile bands. If this opposition is limited to merely what the garrison can effect, then the result must be little indeed, for the garrisons of such places are generally weak and usually consist of infantry only, and that not of the best quality. The idea gains a little more reality if small columns keep themselves in communication with the place, making it their base and place of retreat in case of necessity.
10. As the focus of a general arming of the nation. Provisions, arms, and munitions can never be supplied in a regular manner in a People’s War; on the other hand, it is just in the very nature of such a war to do the best we can; in that way a thousand small sources furnishing means of resistance are opened which otherwise might have remained unused; and it is easy to see that a strong commodious fortress, as a great magazine of these things, can well give to the whole defence more force and intensity, more cohesion, and greater results.
Besides, a fortress is a place of refuge for wounded, the seat of the civil functionaries, the treasury, the point of assembly for the greater enterprises, etc., etc.; lastly, a nucleus of resistance which during the siege places the enemy’s force in a condition which facilitates and favours the attacks of national levies acting in conjunction.
11. For the defence of rivers and mountains. Nowhere can a fortress answer so many purposes, undertake to play so many parts, as when it is situated on a great river. It secures the passage at any time at that spot, and hinders that of the enemy for several miles each way, it commands the use of the river for commercial purposes, receives all ships within its walls, blocks bridges and roads, and helps the indirect defence of the river, that is, the defence by a position on the enemy’s side. It is evident that, by its influence in so many ways, it very greatly facilitates the defence of the river, and may be regarded as an essential part of that defence.
Fortresses in mountains are important in a similar manner. They there form the knots of whole systems of roads, which have their commencement and termination at that spot; they thus command the whole country which is traversed by these roads, and they may be regarded as the true buttresses of the whole defensive system.
CHAPTER XI.
Fortresses (Continued)
We have discussed the object of fortresses: now for their situation. At first the subject seems very complicated, when we think of the diversity of objects, each of which may again be modified by the locality; but such a view has very little foundation if we keep to the essence of the thing, and guard against unnecessary subtilties.
It is evident that all these demands are at once satisfied, if, in those districts of country which are to be regarded as the theatre of war, all the largest and richest towns on the great high roads connecting the two countries with each other are fortified, more particularly those adjacent to harbours and bays of the sea, or situated on large rivers and in mountains. Great towns and great roads always go hand in hand, and both have also a natural connection with great rivers and the coasts of the sea, all these four conditions, therefore, agree very well with each other, and give rise to no incongruity; on the other hand, it is not the same with mountains, for large towns are seldom found there. If, therefore, the position and direction of a mountain chain makes it favourable to a defensive line, it is necessary to close its roads and passes by small forts, built for this purpose only, and at the least possible cost, the great outlay on works of fortification being reserved for the important places of arms in the level country.