follows,—viz.: geographic lines which by their permanent importance belong to the decisive points1 of the theater of war, and those which have value merely because they connect two strategic points.
To prevent confusion, we will elsewhere treat of strategic lines in their relations to maneuvers,—confining ourselves here to what relates to the decisive and objective points of the zone of operations upon which enterprises occur.
Although these are most intimately connected, since every objective point ought necessarily to be one of the decisive points of the theater of war, there is nevertheless a distinction between them; for all decisive points cannot be at the same time the objective of operations. We will, then, define the first, in order to be more easily guided in our selection of the second.
I think the name of decisive strategic point should be given to all those which are capable of exercising a marked influence either upon the result of the campaign or upon a single enterprise. All points whose geographical position and whose natural or artificial advantages favor the attack or defense of a front of operations or of a line of defense are included in this number; and large, well-located fortresses occupy in importance the first rank among them.
The decisive points of a theater of war are of several kinds. The first are the geographic points and lines whose importance is permanent and a consequence of the configuration of the country. For example, take the case of the French in Belgium: whoever is master of the line of the Meuse will have the greatest advantages in taking possession of the country; for his adversary, being outflanked and inclosed between the Meuse and the North Sea, will be exposed to the danger of total ruin if he give battle parallel to that sea.2 Similarly, the valley of the Danube presents a series of important points which have caused it to be looked upon as the key of Southern Germany.