easons, both of which enter materially into
the conduct of naval war. You cannot conquer sea because it is not
susceptible of ownership, at least outside territorial waters. You cannot,
as lawyers say, "reduce it into possession," because you cannot exclude
neutrals from it as you can from territory you conquer. In the second
place, you cannot subsist your armed force upon it as you can upon enemy's
territory. Clearly, then, to make deductions from an assumption that
command of the sea is analogous to conquest of territory is unscientific,
and certain to lead to error.

The only safe method is to inquire what it is we can secure for ourselves,
and what it is we can deny the enemy by command of the sea. Now, if we
exclude fishery rights, which are irrelevant to the present matter, the
only right we or our enemy can have on the sea is the right of passage; in
other words, the only positive value which the high seas have for national
life is as a means of communication. For the active life of a nation such
means may stand for much or it may stand for little, but to every maritime
State it has some value. Consequently by denying an enemy this means of
passage we check the movement of his national life at sea in the same kind
of way that we check it on land by occupying his territory. So far the
analogy holds good, but no further.

So much for the positive value which the sea has in national life. It has
also a negative value. For not only is it a means of communication, but,
unlike the means of communication ashore, it is also a barrier. By winning
command of the sea we remove that barrier from our own path, thereby
placing ourselves in position to exert direct military pressure upon the
national life of our enemy ashore, while at the same time we solidify it
against him and prevent his exerting direct military pressure upon
ourselves.

Command of the sea, therefore, means nothing but the control of maritime
communications, whether for commercial or military purposes. The object of
naval warfare is the control of communications, and not, as in land
warfare, the conquest of territory. The difference is fundamental. True, it
is rightly said that strategy ashore is mainly a question of
communications, but they are communications in another sense. The phrase
refers to the communications of the army alone, and not to the wider
communications which are part of the life of the nation.

But on land also there are communications