As regards the first question, in order to place it in a clearer light we shall merely instance the relation of the south of Germany to France, that is, to the upper Rhine. If, without reference to the number of separate states composing this district of country, we suppose it a whole which is to be fortified strategically, much doubt will arise, for a great number of very fine roads lead from the Rhine into the interior of Franconia, Bavaria and Austria. Certainly, towns are not wanting which surpass others in size and importance, as Nuremburg, Wurzburg, Ulm, Augsburg, and Munich; but if we are not disposed to fortify all, there is no alternative but to make a selection. If, further, in accordance with our view, the fortification of the greatest and wealthiest is held to be the principal thing, still it is not to be denied that, owing to the distance between Nuremburg and Munich, the first has a very different strategic signification from the second; and therefore it always remains to be considered whether it would not be better, in place of Nuremburg, to fortify some other place in the neighbourhood of Munich, even if the place is one of less importance in itself.
As concerns the decision in such cases, that is, answering the first question, we must refer to what has been said in the chapters on the general plan of defence, and on the choice of points of attack. Wherever the most natural point of attack is situated, there the defensive arrangements should be made by preference.
Therefore, amongst a number of great roads leading from the enemy’s country into ours, we should first of all fortify that which leads most directly to the heart of our dominions, or that which, traversing fertile provinces, or running parallel to navigable rivers, facilitates the enemy’s undertaking, and then we may rest secure. The assailant then encounters these works, or should he resolve to pass them by, he will naturally offer a favourable opportunity for operations against his flank.