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.
Over and above the considerations already noticed, there are three others, all of which favour the security of our trade by permitting a much more extended choice of route. The first is, that steam vessels are not forced by prevailing winds to keep to particular courses. The second is, that the improvements in the art of navigation no longer render it so necessary to make well-known landfalls during transit. The third is, that the multiplication of our great ports of distribution have divided the old main flow of trade to the Channel into a number of minor streams that cover a much wider area and demand a greater distribution of force for effective attack. It will be obvious that the combined effect of these considerations is to increase still further the chances of individual vessels evading the enemy's cruisers and to lessen the risk of dispensing with escort.