It was not till three months after the danger of in vasion was practically over that the Battle of Trafalgar was fought. It was fought because Villeneuve had failed; he was superseded, and learning the fact before the arrival of his successor, who was to take the fleet again to the Mediterranean, he determined to run all risks and take the fleet through the Straits of Gibraltar himself. But Nelson was waiting, and by destroying a large part of the French fleet prevented a recurrence of the threat of invasion.
Thus the sea was used as a defence by the men who knew it against those who, like Villeneuve, felt that they were not as familiar with it as were their opponents, or those who, like Napoleon, were unable to understand the peculiar conditions of sea warfare; and Britain for a century was not even threatened by invasion.
(iv) Napoleon, then, was unable to carry an army across the Channel, and had to attempt to conquer the ocean by the land. To do this all the world that counted must be united against Britain, and he set himself to reduce Europe to his will. Even by the date of Trafalgar his troops were far into the heart of Europe, and a few days longer saw Austria at his feet. Prussia succumbed by the end of 1806.
The struggle then at last became a question of resources—of accumulated energy. Napoleon endea voured to shut out Britain from all profits to be made in the markets of the Continent ; even ships not British which came from Britain were to be seized. Britain attempted to shut out France and her conquests from all traffic on the sea, except such as had come from a British port and had paid duty to her. In 1807 the British design was the most successful, for Napoleon was engaged in bringing Russia into line with the other European states, and soldiers could not be spared to enforce the French edicts ; while the fleets of Denmark and Portugal were withdrawn under British persua sion before these lands were finally coerced by French troops.
When Napoleon at last gained control of all Europe but Sweden and Turkey, the position of Britain seemed much more hopeless, but she only declared that all foreign trade must be through Britain, and that dues must be paid; this she enforced by means of her fleet.
Thus not only was Britain strengthened by taking a percentage of all external European trade, but she tended to weaken Napoleon in two ways. In the first place, it was to the interest of the peoples of, at any rate, the northern European lands to trade with Britain, even under the British restrictions ; traffic did take place, and Napoleon alienated the sympathies of these peoples by stopping the illegal trade by means of his troops. In the second place, it was the need which Napoleon felt of preventing British trade with the North of Europe that compelled him to spread his best soldiers all along a fifty-mile-wide belt of coast there, and prevented him sending sufficient force to repel the English military attack on the Peninsula.
He was on the horns of a; dilemma. If he withdrew his troops from Northern Europe to oppose Britain in Spain, then Britain continued to renew her resources by trade in the north. If he kept his troops in the north —as, in fact, he did—he had not enough men to drive the British out of Portugal. His resources of men were scattered, and could effect little. France became poorer and poorer; all commodities became dearer as they were brought nearer to France, for they were more easily imported, and therefore cheaper, as the distance from France increased.
Even the military attack under which Napoleon fell was directly due to the policy forced on him by the fact that Britain was a defended island open to the ocean; for Russia, far removed from France, while agreeing to exclude British shipping, would not agree to exclude British goods brought by other vessels. This was fatal to Napoleon's plans ; a quarrel ensued; the disastrous expedition to Russia followed. The governments of Prussia and Austria, supported by the whole people, took courage again. Napoleon continued to lose ground, for his energies, human and material, were exhausted; finally the allies entered Paris, and the game was up. Ocean power had proved too strong.