Much has been written to prove that the sole reason for the possession of the paramount navy by Great Britain is that the soil of Great Britain cannot support her people.  In an essay, entitled “Naval Power,” which I contributed to the United States Naval Institute in 1911, the fallacy of this was shown; and it was pointed out that even if Great Britain grew more than enough to feed her people, life could be made unendurable to the 60,000,000 living there (or to the people in any civilized and isolated country) by an effective blockading fleet. The question of how great a navy any country needs depends, not on the size, but on the policies of that country, and on the navies of the countries that may oppose those policies.  The navy that a country needs is a navy that can defend its policies, both offensively and defensively.  If, for instance, the United States does not wish to enforce any policy that Great Britain would oppose, or to oppose any policy that Great Britain would enforce, then we may leave her navy out of consideration.  But if we decide that we must maintain a certain policy which a certain country may oppose, then we must have a navy at least equal to hers; because we do not know whether we should have to meet that navy near our coast, or near hers, or far away from both.  For the reason, furthermore, that a war with a European Power might occur at a period of strained relations with some Asiatic Power, we must realize the temptation to that Asiatic Power to seize the opportunity and attack us on the Pacific side, knowing that we should need all our navy on the Atlantic side.  This seems to mean that in order to have an effective naval defense (since we are precluded by our policy from having European allies and no South American country could give us any effective naval help) we must have on each ocean a fleet as strong as that of any nation on that ocean against whose wishes we may have to enforce a policy—­or against whose policy we may have to oppose resistance.

The essential requirement of any defense is that it shall be adequate; because an inadequate defense will be broken down, while the attack will retain a large proportion of its original strength.  In the United States Naval Institute, in 1905, the present writer showed, by means of a series of tables, how, when two forces fight, the force which is originally the more powerful will become gradually more powerful, relatively to the weaker, as the fight goes on.  That, for instance, if two forces start with the relative powers of 10 and 8, the weaker force will be reduced so much more rapidly than the stronger that when it has been reduced to zero the stronger force will have a value of 5.69.  The values mentioned indicated the actual fighting strength—­strength made up of all the factors—­material, physical, and psychic—­that constituted it.  Of course, none of these factors can ever be accurately compared; but nevertheless the tables seemed to prove that in a contest between two forces whose total strengths are as 10 and 8 one force will be reduced to zero, while the other will be reduced not quite one-half.