Such, then, are the abstract conclusions at which we arrive in our attempt
to analyse the idea of command of the sea and to give it precision as the
control of common communications. Their concrete value will appear when we
come to deal with the various forms which naval operations may take, such
as, "seeking out the enemy's fleet," blockade, attack and defence of trade,
and the safeguarding of combined expeditions. For the present it remains to
deal with the various kinds of sea command which flow from the
communication idea.

If the object of the command of the sea is to control communications, it is
obvious it may exist in various degrees. We may be able to control the
whole of the common communications as the result either of great initial
preponderance or of decisive victory. If we are not sufficiently strong to
do this, we may still be able to control some of the communications; that
is, our control may be general or local. Obvious as the point is, it needs
emphasising, because of a maxim that has become current that "the sea is
all one." Like other maxims of the kind, it conveys a truth with a trail of
error in its wake. The truth it contains seems to be simply this, that as a
rule local control can only avail us temporarily, for so long as the enemy
has a sufficient fleet anywhere, it is theoretically in his power to
overthrow our control of any special sea area.

It amounts indeed to little more than a rhetorical expression, used to
emphasise the high mobility of fleets as contrasted with that of armies and
the absence of physical obstacles to restrict that mobility. That this
vital feature of naval warfare should be consecrated in a maxim is well,
but when it is caricatured into a doctrine, as it sometimes is, that you
cannot move a battalion oversea till you have entirely overthrown your
enemy's fleet, it deserves gibbeting. It would be as wise to hold that in
war you must never risk anything.