these communications open can have only one result, viz. the loss of the parts with which communication cannot be maintained.  Experience of war as well as reason will have made it evident that inability to keep open sea-communications cannot be limited to any single line, because the inability must be due either to incapacity in the direction of hostilities or insufficiency of force.  If we have not force enough to keep open all the communications of our widely extended empire, or if—­having force enough—­we are too foolish to employ it properly, we do not hold the command of the sea, and the empire must fall if seriously attacked.

The strategic command of the sea in a particular war or campaign has equal concern for all maritime belligerents.  Before seeing what it is, it will be well to learn on high authority what it is not.  Mahan says that command, or, to use his own term, ’control of the sea, however real, does not imply that an enemy’s single ships or small squadrons cannot steal out of port, cannot cross more or less frequented tracts of ocean, make harassing descents upon unprotected points of a long coast-line, enter blockaded harbours.  On the contrary, history has shown that such evasions are always possible, to some extent, to the weaker party, however great the inequality of naval strength.’[55] The Anglo-French command of the sea in 1854-56, complete as it was, did not enable the allies to intercept the Russian ships in the North-Western Pacific, nor did that held by the Federals in the American civil war put an early stop to the cruises of the Confederate vessels.  What the term really does imply is the power possessed from the first, or gained during hostilities, by one belligerent of carrying out considerable over-sea expeditions at will.  In the Russian war just mentioned the allies had such overwhelmingly superior sea-power that the Russians abandoned to them without a struggle the command of the sea; and the more recent landing in South Africa, more than six thousand miles away, of a large British army without even a threat of interruption on the voyage is another instance of unchallenged command.  In wars between great powers and also between secondary powers, if nearly equally matched, this absence of challenge is rare.  The rule is that the command of the sea has to be won after hostilities begin.  To win it the enemy’s naval force must be neutralised.  It must be driven into his ports and there blockaded or ‘masked,’ and thus rendered virtually innocuous; or it must be defeated and destroyed.  The latter is the preferable, because the more effective, plan.  As was perceptible in the Spanish-American war of 1898, as long as one belligerent’s fleet is intact or at large, the other is reluctant to carry out any considerable expedition over-sea.  In fact, the command of the sea has not been secured whilst the enemy continues to have a ’fleet in being.’[56]

[Footnote 55:  Influenceof_Sea-power_on_History_, 1890, p. 4.]