can occupy and appropriate. The sea is not territory. It is not
nor can it be made subject to the authority of an enemy in the same
sense that the land can, nor does it possess any resources in itself
such as on the land can be appropriated to the disadvantage and ultimate
discomfiture of a belligerent whose territory has been invaded. The sea
is the common highway of all nations, and the exclusive possession of
none. Apart from its fisheries, which, outside the territorial waters of
any particular State, are open to all nations, it is of no use, except
as a highway, to any State. But its use as a highway is the root of all
sea power, the foundation of all naval warfare. It is only by this
highway that an island State can be invaded, only by this highway that
an island State, or a State having no common frontier with its
adversary, can encounter and subdue the armed forces of the enemy,
whether on sea or on land.

Moreover, the sea as a highway differs in many important respects from
such highways or other lines of communication as serve for the transit
and transport of armed forces and their necessary supplies on land. In
one sense it is all highway, that is, it can be traversed in every
direction by ships, wherever there is water enough for them to float.
For military purposes land transit is confined to such highways as are
suitable to the march of an army accompanied by artillery and heavy
baggage and supply trains, or to such railways as can more expeditiously
serve the same purpose. Hence an army advancing in an enemy's country
cannot advance on a very broad front, nor can it outmarch its baggage
and other supplies except for a very limited time and for some
exceptional purpose. Sea transport is subject to no such limitations.
Ships carry their own supplies with them, and a fleet of ships, whether
of transports or of warships, can move on as broad a front as is
compatible with the exercise of due control over their combined
movements. Moreover, within certain limits and with certain exceptions,
where the waters to be traversed are narrow, ships and fleets can vary
their line of transit and advance to such an extent as to render the
discovery of their whereabouts a matter of some difficulty. The same
conditions affect the transit of such merchant vessels as, carrying the
flag of one belligerent, are liable to capture by the other. Hence the
primary aim of all naval warfare is and must be so to control the lines
of