Some Principles of Maritime Strategy

by Julian Stafford Corbett

It is hoped that the foregoing sketch of our traditional system of trade defence will avail to raise a doubt whether either assumption can be accepted without very careful consideration. In the history of that system there is no indication that it was affected by the volume of the trade it was designed to protect. Nor has any one succeeded in showing that the pressure which an enemy could exert upon us through our commerce increased in effect with the volume of our seaborne trade. The broad indications indeed are the other way—that the greater the volume of our trade, the less was the effective impression which an enemy could make upon it, even when he devoted his whole naval energies to that end. It is not too much to say that in every case where he took this course his own trade dwindled to nothing, while ours continually increased.

It may be objected that this was because the only periods in which he devoted his main efforts to trade destruction were when we had dominated his navy, and being no longer able to dispute the command, he could do no more than interfere with its exercise. But this must always be so whether we have positively dominated his navy or not. If he tries to ignore our battle-fleets, and devotes himself to operations against trade, he cannot dispute the command. Whatever his strength, he

must leave the command to us. He cannot do both systematically, and unless he attacks our trade systematically by sustained strategical operation, he cannot hope to make any real impression.

If, now, we take the two assumptions and test them by the application of elementary principles, both will appear theoretically unsound. Let us take first the relation of vulnerability to volume. Since the object of war is to force our will upon the enemy, the only way in which we can expect war on commerce to serve our end is to inflict so much damage upon it as will cause our enemy to prefer peace on our terms to a continuation of the struggle. The pressure on his trade must be insupportable, not merely annoying. It must seriously cripple his finance or seriously threaten to strangle his national life and activities. If his total trade be a hundred millions, and we succeed in destroying five, he will feel it no more than he does the ordinary fluctuations to which he is accustomed in time of peace. If, however, we can destroy fifty millions, his trade equilibrium will be overthrown, and the issue of the war will be powerfully affected. In other words, to affect the issue the impression made on trade must be a percentage or relative impression. The measure of a nation's vulnerability through its trade is the percentage of destruction that an enemy can effect.

Now, it is true that the amount of damage which a belligerent can inflict with a given force on an enemy's commerce will vary to some extent with its volume; for the greater the volume of commerce, the more fertile will be the undefended cruising grounds. But no matter how fertile such areas might be, the destructive power of a cruiser was always limited, and it must be still more limited in the future. It was limited by the fact that it was physically impossible to deal with more than a certain number of prizes in a certain time, and, for the reasons already indicated, this limit has suffered a very marked restriction. When this limit of capacity in a given

force is passed, the volume of commerce will not affect the issue; and seeing how low that capacity must be in the future and how enormous is the volume of our trade, the limit of destructive power, at least as against ourselves, provided we have a reasonably well-organised system of defence, must be relatively low. It must, in fact, be passed at a percentage figure well within what we have easily supported in the past. There is reason, therefore, to believe that so far from the assumption in question being true, the effective vulnerability of sea-borne trade is not in direct but in inverse proportion to its volume. In other words, the greater the volume, the more difficult it is to make an effective percentage impression.

Similarly, it will be observed that the strain of trade defence was proportioned not to the volume of that trade, but to the number and exposure of its terminals and focal points. Whatever the volume of the trade these remained the same in number, and the amount of force required for their defence varied only with the strength that could readily be brought to bear against them. It varied, that is, with the distribution of the enemy's bases and the amount of his naval force. Thus in the war of 1812 with the United States, the West Indian and North American areas were much more exposed than they had been when we were at war with France alone and when American ports were not open to her as bases. They became vulnerable not only to the United States fleet, but also in a much higher degree to that of France, and consequently the force we found necessary to devote to trade defence in the North Atlantic was out of all proportion to the naval strength of the new belligerent. Our protective force had to be increased enormously, while the volume of our trade remained precisely the same.

This relation of trade defence to terminal and focal areas is of great importance, for it is in the increase of such areas in the Far East that lies the only radical change in the problem.

The East Indian seas were always of course to some extent treated as a defended area, but the problem was simplified by the partial survival in those regions of the old method of defence. Till about the end of the seventeenth century long-range trade was expected to defend itself, at least outside the home area, and the retention of their armament by East Indiamen was the last survival of the practice. Beyond the important focal area of St. Helena they relied mainly on their own power of resistance or to such escort as could be provided by the relief ships of the East Indian station. As a rule, their escort proper went no farther outward-bound than St. Helena, whence it returned with the homeward-bound vessels that gathered there from India, China, and the South Sea whaling grounds. The idea of the system was to provide escort for that part of the great route which was exposed to attack from French or Spanish colonial bases on the African coasts and in the adjacent islands.

For obvious reasons this system would have to be reconsidered in the future. The expansion of the great European Powers have changed the conditions for which it sufficed, and in a war with any one of them the system of defended terminal and focal areas would require a great extension eastward, absorbing an appreciable section of our force, and entailing a comparatively weak prolongation of our chain of concentrations. Here, then, we must mark a point where trade defence has increased in difficulty, and there is one other.