easure 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