In the years immediately following 1805, Great Britain in self-defence, or as a means of continuing the war against France, in regard to which her resources for operations on land were limited, had recourse to the operations of blockade, by which the sea was closed, as far as possible, to enemy merchantmen while Great Britain prohibited neutral ships from carrying enemy goods. Napoleon replied by the attempt to exclude British goods from the Continent altogether, and indeed the pressure produced by Great Britain's blockades compelled Napoleon further to extend his domination on the Continent. Thus the other continental States found themselves between the devil and the deep sea. They had to submit to the domination of Napoleon on land and to the complete ascendency of Great Britain on the waters which surrounded their coasts. The British claims to supremacy at sea were unanimously resented by all the continental States, which all suffered from them, but in all cases the national resentment against French invasion or French occupation of territory was greater than the resentment against the invisible pressure exercised by the British navy. In the wars of liberation, though Great Britain was the welcome ally of all the States that were fighting against France, the pressure of British sea power was none the less disagreeable and, in the years of peace which followed, the British monopoly of sea power, of sea-carriage, of manufacturing industry, and of international trade were equally disliked by almost all the nations of Europe. Protective duties were regarded as the means of fostering national industries and of sheltering them against the overpowering competition of British manufactures. The British claim to the dominion of the sea was regarded as unfounded in right, and was in principle as strongly denounced as had been the territorial domination of France. The mistress of the seas was regarded as a tyrant, whom it would be desirable, if it were possible, to depose, and there were many who thought that as the result of a conflict in which the final success had been gained by the co-operation of a number of States acting together, the gains of Great Britain which, as time went on, were seen to be growing into a world-wide empire, had been out of proportion to the services she had rendered to the common cause. Meantime during the century which has elapsed since the last great war, there has been a complete change in the conditions of intercourse between nations at sea and of maritime warfare. It has come about gradually, almost imperceptibly, so that it could hardly be appreciated before the close of the nineteenth century. But it is vital to Great Britain that her people should understand the nature of the transformation.