We have seen that blockade is only a means to an end, that end being the destruction or surrender of the armed forces of the enemy. We have seen also that that end cannot be obtained by blockade alone. All that a military blockade can do is by a judicious disposition of superior force, either to prevent the enemy coming out at all, or to secure that if he does come out he shall be brought to action. The former method is only applicable where the blockader's superiority of force is so great that his adversary cannot venture at the outset to encounter his main fleets in the open, and in that case the establishment of a blockade of this character is for many purposes practically tantamount to securing the command of the sea to the blockader so long as the blockade can be maintained. Such a situation, however, can very rarely arise. There are very few instances of it in naval history, and there are likely to be fewer in the future than there have been in the past. The closest blockade ever established and maintained was that of Brest by Cornwallis from 1803 to 1805, when Napoleon was projecting the invasion of England. Yet it would be too much to say that during those strenuous years Ganteaume never could have got out, had he been so minded, and it is not to be forgotten that for some time during the crisis of the campaign he was forbidden by Napoleon to make the attempt. Moreover, such a situation, even when it does arise, amounts at best to a stalemate, not to a checkmate. It leaves the enemy's fleet "a fleet in being," immobilized and wiped off the board for the moment, but nevertheless so operating as to immobilize the blockading fleet in so far as the chief effort of the latter must be concentrated on maintaining the blockade.