Lines are strategic either from their geographical position or from their relation to temporary maneuvers. The first class may be subdivided as follows,--viz.: geographic lines which by their permanent importance belong to the decisive points[7] 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.[8] 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. Those points the possession of which would give the control of the junction of several valleys and of the center of the chief lines of communication in a country are also _decisive geographic points_. For instance, Lyons is an important strategic point, because it controls the valleys of the Rhone and Saône, and is at the center of communications between France and Italy and between the South and East; but it would not be a _decisive_ point unless well fortified or possessing an extended camp with _têtes de pont_. Leipsic is most certainly a strategic point, inasmuch as it is at the junction of all the communications of Northern Germany. Were it fortified and did it occupy both banks of the river, it would be almost the key of the country,--if a country has a key, or if this expression means more than a decisive point.