But beyond all this there lies in the theory of war yet another element of peculiar value to a maritime Empire. We are accustomed, partly for convenience and partly from lack of a scientific habit of thought, to speak of naval strategy and military strategy as though they were distinct branches of knowledge which had no common ground. It is the theory of war which brings out their intimate relation. It reveals that embracing them both is a larger strategy which regards the fleet and army as one weapon, which co-ordinates their action, and indicates the lines on which each must move to realise the full power of both. It will direct us to assign to each its proper function in a plan of war; it will enable each service to realise the better the limitations and the possibilities of the function with which it is charged, and how and when its own necessities must give way to a higher or more pressing need of the other. It discloses, in short, that naval strategy is not a thing by itself, that its problems can seldom or never be solved on naval considerations alone, but that it is only a part of maritime strategy--the higher learning which teaches us that for a maritime State to make successful war and to realise her special strength, army and navy must be used and thought of as instruments no less intimately connected than are the three arms ashore.
It is for these reasons that it is of little use to approach naval strategy except through the theory of war. Without such theory we can never really understand its scope or meaning, nor can we hope to grasp the forces which most profoundly affect its conclusions.
The last thing that an explorer arrives at is a complete map that will cover the whole ground he has travelled, but for those who come after him and would profit by and extend his knowledge his map is the first thing with which they will begin. So it is with strategy. Before we start upon its study we seek a chart which will show us at a glance what exactly is the ground we have to cover and what are the leading features which determine its form and general characteristics. Such a chart a "theory of war" alone can provide. It is for this reason that in the study of war we must get our theory clear before we can venture in search of practical conclusions. So great is the complexity of war that without such a guide we are sure to go astray amidst the bewildering multiplicity of tracks and obstacles that meet us at every step. If for continental strategy its value has been proved abundantly, then for maritime strategy, where the conditions are far more complex, the need of it is even greater.