On War

by Carl von Clausewitz

It is easily seen that impassable forests and marshes have a similar effect to that of rivers.

The question has been often raised as to whether towns situated in a very difficult country are well or ill suited for fortresses. As they can be fortified and defended at a small expense, or be made much stronger, often impregnable, at an equal expenditure, and the services of a fortress are always more passive than active, it does not seem necessary to attach much importance to the objection that they can easily be blockaded.

If we now, in conclusion, cast a retrospective glance over our simple system of fortification for a country, we may assert that it rests on comprehensive data, lasting in their nature, and directly connected with the foundations of the state itself, not on transient views on war, fashionable for a day; not on imaginary strategic niceties, nor on requirements completely singular in character an error which might be attended with irreparable consequences if allowed to influence the construction of fortresses intended to last five hundred, perhaps a thousand, years. Silberberg, in Silesia, built by Frederick the Great on one of the ridges of the Sudetics, has, from the complete alteration in circumstances which has since taken place, lost almost entirely its importance and object, whilst Breslau, if it had been made a strong place of arms, and continued to be so, would have always maintained its value against the French, as well as against the Russians, Poles, and Austrians.

Our reader will not overlook the fact that these considerations are not raised on the supposed case of a state providing itself with a set of new fortifications; they would be useless if such was their object, as such a case seldom, if ever, happens; but they may all arise at the designing of each single fortification.

CHAPTER XII.
Defensive Position

Every position in which we accept battle, at the same time making use of the ground as a means of protection, is a defensive position, and it makes no difference in this respect whether we act more passively or more offensively in the action. This follows from the general view of the defensive which we have given.

Now we may also apply the term to every position in which an army whilst marching to encounter the enemy would certainly accept battle if the latter sought for it. In point of fact, most battles take place in this way, and in all the middle ages no other was ever thought of. That is, however, not the kind of position of which we are now speaking; by far the greater number of positions are of this kind, and the conception of a position in contradistinction to a camp taken up on the march would suffice for that. A position which is specially called a defensive position must therefore have some other distinguishing characteristics.

In the decisions which take place in an ordinary position, the idea of time evidently predominates; the armies march against each other in order to come to an engagement: the place is a subordinate point, all that is required from it is that it should not be unsuitable. But in a real defensive position the idea of place predominates; the decision is to be realised on this spot, or rather, chiefly through this spot. That is the only kind of position we have here in view.

Now the connection of place is a double one; that is, in the first instance, inasmuch as a force posted at this point exercises a certain influence upon the war in general; and next, inasmuch as the local features of the ground contribute to the strength of the army and afford protection: in a word, a strategic and a tactical connection.

Strictly speaking, the term defensive position has its origin only in connection with tactics, for its connection with strategy, namely, that an army posted at this point by its presence serves to defend the country, will also suit the case of an army acting offensively.