By the theory of naval war it must be reiterated we mean nothing but an enunciation of the fundamental principles which underlie all naval war. Those principles, if we have determined them correctly, should be found giving shape not only to strategy and tactics, but also to material, whatever method and means of naval warfare may be in use at any given time. Conversely, if we find strategy, tactics, or organisation exhibiting a tendency to reproduce the same forms under widely differing conditions of method and material, we should be able to show that those forms bear a constant and definite relation to the principles which our theory endeavours to express. In the case of Anson's threefold organisation, the relation is not far to seek, though it has become obscured by two maxims. The one is, that "the command of the sea depends upon battleships," and the other, that "cruisers are the eyes of the fleet." It is the inherent evil of maxims that they tend to get stretched beyond their original meaning. Both of these express a truth, but neither expresses the whole truth. On no theory of naval warfare can we expect to command the sea with battleships, nor, on the communication theory, can we regard the primary function of cruisers as being to scout for a battle-fleet. It is perfectly true that the control depends ultimately on the battle-fleet if control is disputed by a hostile battle-fleet, as it usually is. It is also true that, so far as is necessary to enable the battle-fleet to secure the control, we have to furnish it with eyes from our cruiser force. But it does not follow that this is the primary function of cruisers. The truth is, we have to withdraw them from their primary function in order to do work for the battle-fleet which it cannot do for itself.