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