For naval purposes these three ideas are best described by the term "lines of passage and communication," which were in use at the end of the 18th century, and they may be regarded as those waters over which passes the normal course of vessels proceeding from the base to the objective or the force to be supplied. _Maritime Communications_ The various kinds of Maritime Communications for or against which a fleet may have to operate are:-- (1) Its own communications, or those of its adversary (which correspond to the communications of armies operating ashore). These have greatly increased in importance strategically with the increased dependence of modern fleets on a regular supply of coals, stores, ammunition, &c. (2) The communications of an army operating from an advanced oversea base, that is, communication between the advanced and the main base. (3) Trade Routes, that is, the communications upon which depend the national resources and the supply of the main bases, as well as the "lateral" or connecting communications between various parts of belligerents' possessions. In Land Strategy the great majority of problems are problems of communication. Maritime Strategy has never been regarded as hinging on communications, but probably it does so, as will appear from a consideration of Maritime Communications, and the extent to which they are the main preoccupation of naval operations; that is to say, all problems of Naval Strategy can be reduced to terms of "passage and communication," and this is probably the best method of solving them. * * * * * PART TWO NAVAL STRATEGY CONSIDERED AS A QUESTION OF PASSAGE AND COMMUNICATION NAVAL STRATEGY DEFINED By "Naval Strategy" we mean the art of conducting the major operations of the fleet. Such operations have for their object "passage and communication"; that is, the fleet is mainly occupied in guarding our own communications and seizing those of the enemy. We say the aim of Naval Strategy is to get command of the sea. This means something quite different from the military idea of occupying territory, for the sea cannot be the subject of political dominion or ownership. We cannot subsist upon it (like an army on conquered territory), nor can we exclude neutrals from it. The value of the sea in the political system of the world is as a means of communication between States and parts of States. Therefore the "command of the sea" means the control of communications in which the belligerents are adversely concerned. The command of the sea can never be, like the conquest of territory, the ulterior object of a war, unless it be a purely maritime war, as were approximately our wars with the Dutch in the 17th century, but it may be a primary or immediate object, and even the ulterior object of particular operations. History shows that the actual functions of the fleet (except in purely maritime wars) have been threefold:--