For the purpose, then, of framing a plan of war or campaign, it must be taken that command may exist in various states or degrees, each of which has its special possibilities and limitations.  It may be general or local, and it may be permanent or temporary.  General command may be permanent or temporary, but mere local command, except in very favourable geographical conditions, should scarcely ever be regarded as more than temporary, since normally it is always liable to interruption from other theatres so long as the enemy possesses an effective naval force.

Finally, it has to be noted that even permanent general command can never in practice be absolute.  No degree of naval superiority can ensure our communications against sporadic attack from detached cruisers, or even raiding squadrons if they be boldly led and are prepared to risk destruction.  Even after Hawke’s decisive victory at Quiberon had completed the overthrow of the enemy’s sea forces, a British transport was captured between Cork and Portsmouth, and an Indiaman in sight of the Lizard, while Wellington’s complaints in the Peninsula of the insecurity of his communications are well known.[9] By general and permanent control we do not mean that the enemy can do nothing, but that he cannot interfere with our maritime trade and oversea operations so seriously as to affect the issue of the war, and that he cannot carry on his own trade and operations except at such risk and hazard as to remove them from the field of practical strategy.  In other words, it means that the enemy can no longer attack our lines of passage and communication effectively, and that he cannot use or defend his own.

  [9] In justice to Wellington, it should be said that his complaints were
  due to false reports that exaggerated a couple of insignificant captures
  into a serious interruption.

To complete our equipment for appreciating any situation for which operations have to be designed, it is necessary to remember that when the command is in dispute the general conditions may give a stable or an unstable equilibrium.  It may be that the power of neither side preponderates to any appreciable extent.  It may also be that the preponderance is with ourselves, or it may be that it lies with the enemy.  Such preponderance of course will not depend entirely on actual relative strength, either physical or moral, but will be influenced by the inter-relation of naval positions and the comparative convenience of their situation in regard to the object of the war or campaign.  By naval positions we mean, firstly, naval bases and, secondly, the terminals of the greater lines of communication or trade-routes and the focal areas where they tend to converge, as at Finisterre, Gibraltar, Suez, the Cape, Singapore, and many others.