communication which traverse the seas affected, that the enemy
cannot move his warships from one point to another without encountering
a superior force of his adversary, and that his merchant ships cannot
prosecute their voyages without running extreme risk of capture by the
way. This is called, in time-honoured phraseology, securing the command
of the sea, and the true meaning of this phrase is nothing more nor less
than the effective control of all such maritime communications as are or
can be affected by the operations of either belligerent. This control
may extend, according to circumstances, to all the navigable seas of the
globe, or it may be confined, for all practical purposes, to the waters
adjacent to the respective territories of the two belligerents. In
theory, however, its effect is unlimited, and so it must be in practice,
where the territories of one belligerent or the other are widely
scattered over the globe. That is the sense in which "the sea is all
one."

It is important to note that the phrase "command of the sea" has no
definite meaning except in war. In time of peace no State claims to
command the sea or to control it in any way. But in any war in which
naval force is engaged each belligerent seeks to secure the command of
the sea for himself and to deny it to his enemy, that is to close the
highway which the sea affords in time of peace to his warships and his
merchant vessels alike. As regards the enemy's warships, moreover, he
seeks to secure his own command by their destruction or capture. This is
not always possible, because if the naval forces of the two belligerents
are very unequally matched, it is always open to the weaker of the two
to decline the conflict by keeping his main fleets in ports unassailable
by naval force alone, and seeking to reduce the superiority of his
adversary by assailing him incessantly with torpedo craft. He may also
attempt the hazardous enterprise of sending out isolated cruisers to
prey upon his adversary's commerce afloat. But in the case supposed,
where the superiority of one side is so great as to compel the main
fleets of the other to seek the protection of their fortified ports,
such an enterprise is, as I shall show in a subsequent chapter, not only
extremely hazardous in itself, but quite incapable of inflicting such
loss on the superior adversary as would be likely to induce him to
abandon the conflict.

Nevertheless the command of the sea is not establ