If we desire to formulate the principles on which this conclusion rests we shall find them in the two broad rules, firstly, that the vulnerability of trade is in inverse ratio to its volume, and secondly, that facility of attack means facility of defence.  The latter, which was always true, receives special emphasis from modern developments.  Facility of attack means the power of exercising control.  For exercise of control we require not only numbers, but also speed and endurance, qualities which can only be obtained in two ways:  it must be at the cost of armour and armament, or at the cost of increased size.  By increasing size we at once lose numbers.  If by sacrificing armament and armour we seek to maintain numbers and so facilitate attack, we at the same time facilitate defence.  Vessels of low fighting power indeed cannot hope to operate in fertile areas without support to overpower the defence.  Every powerful unit detached for such support sets free a unit on the other side, and when this process is once begun, there is no halting-place.  Supporting units to be effective must multiply into squadrons, and sooner or later the inferior Power seeking to substitute commerce destruction for the clash of squadrons will have squadronal warfare thrust upon him, provided again the superior Power adopts a reasonably sound system of defence.  It was always so, and, so far as it is possible to penetrate the mists which veil the future, it would seem that with higher mobility and better means of communication the squadronal stage must be reached long before any adequate percentage impression can have been made by the sporadic action of commerce destroyers.  Ineffectual as such warfare has always been in the past, until a general command has been established, its prospects in the future, judged by the old established principles, are less promising than ever.

Finally, in approaching the problem of trade protection, and especially for the actual determination of the force and distribution it requires, there is a dominant limitation to be kept in mind.  By no conceivable means is it possible to give trade absolute protection.  We cannot make an omelette without breaking eggs.  We cannot make war without losing ships.  To aim at a standard of naval strength or a strategical distribution which would make our trade absolutely invulnerable is to march to economic ruin.  It is to cripple our power of sustaining war to a successful issue, and to seek a position of maritime despotism which, even if it were attainable, would set every man’s hand against us.  All these evils would be upon us, and our goal would still be in the far distance.  In 1870 the second naval Power in the world was at war with an enemy that could not be considered a naval Power at all, and yet she lost ships by capture.  Never in the days of our most complete domination upon the seas was our trade invulnerable, and it never can be.  To seek invulnerability is to fall into the strategical vice of trying to be superior everywhere,