th is, that in all the larger achievements of sea power--those,
that is, to which a combination of naval and military force is
indispensable--it is impossible to disengage the influence of one of
these factors on the final issue from that of the other, and perhaps
idle to attempt do to so. They act, as it were, like a chemical
combination, not like the resultant of two separate but correlated
mechanical forces, and their joint effect may be just as different from
what might be the effect of either acting separately as water is
different from the oxygen and hydrogen of which it is composed. But
their operation in this wise can only begin after the command of the sea
has been secured, or at least has been so far established as to reduce
to a negligible quantity the risk of conducting military operations
across seas of which the command is still nominally in dispute. Now
there are several phases or stages in the enterprise of securing the
command of the sea; but they all depend on the power and the will to
fight for it. There is no absolute command of the sea, except in the
case of hostilities between two belligerents, separated by the sea, one
of whom has no naval force at all. The solitary case in history of this
situation is that of the War in South Africa. A similar situation would
arise if one of two belligerents had completely destroyed all the
effective naval force of the other. But that is a situation of which
history affords few, if any, examples. Between these two extremes lies
the whole history of naval warfare.

There is, moreover, one characteristic of naval warfare which has no
exact counterpart in the conduct of military enterprises on land. This
is the power which a naval belligerent has of withdrawing his sea-going
force out of the reach of the sea-going force of the enemy by placing it
in sheltered harbours too strongly fortified for the enemy to reduce by
naval power alone. The only effective answer to this which the superior
belligerent can make is, as has already been shown, to establish a
blockade of the ports in question. This procedure is analogous to, but
not identical with, the investment by military forces of a fortress in
which an army has found shelter in the interior of the enemy's country.
But the essential difference is that the land fortress can be completely
invested so that no food or other supplies can reach it, whereas a sea
fortress cannot, unless it is situated on a small island, be co