These functions may be discharged in two ways:--
(1) By direct territorial attacks, threatened or performed (bombardment, landing, raiding parties, &c).
(2) By getting command of the sea, _i.e._, establishing ourselves in such a position that we can control the maritime communications of all parties concerned, so that we can operate by sea against their territory, commerce, and allies, and they cannot operate against ours.
NOTE.--The power of the second method, by controlling communications, is out of all proportion to the first--direct attack. Indeed, the first can seldom be performed with any serious effect without the second. Thus, from this point of view also, it is clear that Naval Strategy is mainly a question of communications.
But not entirely. Circumstances have arisen when the Fleet must discharge part of its function by direct action before there is time to get general control of the communications. (That is, political and military considerations may deflect normal operation of Naval Strategy.)
EXAMPLE.--Rooke's capture of Gibraltar in 1704, in the face of the unshaken Toulon Fleet. Japanese invasion of Manchuria.
Command of the sea exists only in a state of war. If we say we have command of the sea in time of peace it is a rhetorical expression meaning that we have (a) adequate Naval positions; (b) an adequate Fleet to secure the command when war breaks out.
(a) _General command_ is secured when the enemy is no longer able to act dangerously against our line of passage and communication or to defend his own, or (in other words) when he is no longer able to interfere seriously with our trade or our military or diplomatic operations.
This condition exists practically when the enemy is no longer able to send squadrons to sea.
NOTE.--Command of the sea does not mean that the enemy can do absolutely nothing, but that he cannot _seriously_ interfere with the undertakings by which we seek to secure the object of the war, or to force our will upon him.
(b) _Local command_ implies a state of things in which we are able to prevent the enemy from interfering with our passage and communication in one or more theatres of operation.
2. Both local and general command may be (a) temporary; (b) permanent.