The military or strategic value of a naval position depends upon its situation, upon its strength, and upon its resources. Of the three, the first is of most consequence, because it results from the nature of things; whereas the two latter, when deficient, can be supplied artificially, in whole or in part. Fortifications remedy the weaknesses of a position, foresight accumulates beforehand the resources which nature does not yield on the spot; but it is not within the power of man to change the geographical situation of a point which lies outside the limit of strategic effect. It is instructive, and yet apparent to the most superficial reading, to notice how the first Napoleon, in commenting upon a region likely to be the scene of war, begins by considering the most conspicuous natural features, and then enumerates the commanding positions, their distances from each other, the relative directions, or, as the sea phrase is, their "bearings," and the particular facilities each offers for operations of war. This furnishes the ground plan, the skeleton, detached from confusing secondary considerations, and from which a clear estimate of the decisive points can be made. The number of such points varies greatly, according to the character of the region. In a mountainous, broken country they may be very many; whereas in a plain devoid of natural obstacles there may be few, or none save those created by man. If few, the value of each is necessarily greater than if many; and if there be but one, its importance is not only unique, but extreme,--measured only by the size of the field over which its unshared influence extends. The sea, until it approaches the land, realizes the ideal of a vast plain unbroken by obstacles. On the sea, says an eminent French tactician, there is no field of battle, meaning that there is none of the natural conditions which determine, and often fetter, the movements of the general. But upon a plain, however flat and monotonous, causes, possibly slight, determine the concentration of population into towns and villages, and the necessary communications between the centres create roads. Where the latter converge, or cross, tenure confers command, depending for importance upon the number of routes thus meeting, and upon their individual value. It is just so at sea. While in itself the ocean opposes no obstacle to a vessel taking any one of the numerous routes that can be traced upon the surface of the globe between two points, conditions of distance or convenience, of traffic or of wind, do prescribe certain usual courses. Where these pass near an ocean position, still more where they use it, it has an influence over them, and where several routes cross near by that influence becomes very great,--is commanding.