depends so much on a fully manned engine-room.  This will tend to jeopardise her chances of return through or near defended areas.  The only escape from this difficulty is to sink the captured ship.  But this course has objections scarcely less weighty than the other.  No Power will incur the odium of sinking a prize with all hands, and their removal to the captor’s ship takes time, especially in bad weather, and the presence of such prisoners in a cruiser in any number soon becomes a serious check on her fighting power.  In the case of large ships, moreover, the work of destruction is no easy matter.  In the most favourable circumstances it takes a considerable time, and thus not only eats into the cruiser’s endurance, but decreases her chances of evasion.

From these and similar considerations it is obvious that the possibilities of operations on the great trade-routes are much less extensive than they were formerly, while to speak of cruisers “infesting” those routes is sheer hyperbole.  Under modern conditions it is scarcely more feasible than it would be to keep up a permanent blockade of the British Islands.  It would require a flow of ships in such numbers as no country but our own can contemplate possessing, and such as could not be maintained without having first secured a very decided preponderance at sea.  The loss of radius of action therefore, though it does not increase the power of defence, sensibly lessens that of attack by pelagic operations.

For the great increase in the powers of defence we must turn to the extraordinary development in the means of distant communication.  Under former conditions it was possible for a cruising ship to remain for days upon a fertile spot and make a number of captures before her presence was known.  But since most large merchantmen have been fitted with wireless installations, she cannot now attack a single one of them without fear of calling down upon her an adversary.  Moreover, when she is once located, every ship within wireless reach can be warned of her presence and avoid her.  She must widely and constantly shift her position, thereby still further reducing her staying power.  On the whole, then, it would appear that in so far as modern developments affect the problem, they certainly render pelagic operations far more difficult and uncertain than they used to be.  Upon the great routes the power of attack has been reduced and the means of evasion has increased to such an extent as to demand entire reconsideration of the defence of trade between terminal areas.  The whole basis of the old system would seem to be involved.  That basis was the convoy system, and it now becomes doubtful whether the additional security which convoys afforded is sufficient to outweigh their economical drawbacks and their liability to cause strategical disturbance.