de is easier and cheaper, and can
accomplish almost everything that an enemy desires, especially
if it be enlivened by the occasional dropping of thousand-pound
shells into Wall Street and the navy-yard.

While, however, the _primary_ use of naval power seems to be to
prevent blockade, a navy, like any other weapon, may be put to
any other uses which circumstances indicate. For instance, the
Northerners in the Civil War used the navy not to prevent blockade,
but to make blockade; the Japanese used the navy to cover the
transportation of their armies to Manchuria and Corea; and Great
Britain has always used her navy to protect her trade routes.

A general statement of the various uses of a navy has been put into
the phrase "command of the sea."

Of course, the probability of getting "command of the sea," or
of desiring to get it is dependent on the existence of a state
of war, and there are some who believe that the probability of
our becoming involved in a war with a great naval nation is too
slight to warrant the expense of money and labor needed to prepare
the necessary naval power. So it may be well to consider what is
the degree of probability.

This degree of probability cannot be determined as accurately as
the probabilities of fire, death, or other things against which
insurance companies insure us; for the reason that wars have been
much less frequent than fires, deaths, etc., while the causes that
make and prevent them are much more numerous and obscure. It seems
clear, however, that, as between two countries of equal wealth,
the probability of war varies with the disparity between their
navies, and unless other nations are involved, is practically zero,
when their navies are equal in power; and that, other factors being
equal, the _greatest probability of war is between two countries,
of which one is the more wealthy and the other the more powerful_.

In reckoning the probability of war, we must realize that _the most
pregnant cause of war is the combination of conflicting interests
with disparity in power_. And we must also realize that it is not
enough to consider the situation as it is now: that it is necessary
to look at least ten years ahead, because it would take the United
States that length of time to prepare a navy powerful enough to
fight our possible foes with reasonable assurance of success.

Ten years, however, is not really far enough ahead to look, for
the simple reason that, while we co