When colonies were first recognized as essential to the prosperity of European nations, the rule was universally observed that only the mother country could trade with her own. In 1756 France endeavored to break this rule by permitting neutral ships to engage in traffic between herself and her West Indian possessions. England at once laid down the "rule of 1756," that neutrals should not exercise in time of war privileges of traffic which they were not permitted to enjoy in time of peace; and this principle she was able to maintain more or less completely until 1793, when France declared war on her, and again invited neutral commerce to French colonial harbors. England, having regained her supremacy of the seas, reasserted in 1793 the rule of 1756, but nevertheless so modified it the following year that she permitted neutral traders to break, in their own or in her harbors, their voyages from or to colonial ports. In 1796 France notified all neutrals that she would treat them just as they permitted Great Britain to treat them, and in 1798 shut all her harbors to any vessel which had even touched at a British port. This state of affairs continued until the peace of Amiens. When war was renewed in 1803 between England and France the former again asserted the rule of 1756 as binding, while indirect trade between neutral ports and the ports of an enemy was again allowed, but under the new proviso that the neutral ship did not on her outward voyage furnish the enemy with goods contraband of war. This privilege of indirect trade was invaluable to American ship-owners, and for two years the ocean commerce of all Europe was in their hands. The fortunes they thus accumulated were enormous, while Great Britain saw her own manufactures displaced by those of continental nations, and the colonies of her enemies prospering as never before. In 1805, therefore, she withdrew the privilege of indirect trade, and her flag being, after Trafalgar, the only belligerent one left on the ocean, proceeded both to enforce the new rule and to abuse the proviso concerning neutral vessels carrying contraband of war by ruthlessly exercising the right of search. Under the orders in council of September fifth, 1805, every neutral ship must be examined to see whether its lading was a cargo of neutral goods, or whether it contained anything contraband. This could only mean that every American ship laden with other than American goods was to be seized; and in May of the following year, by the still more notorious order of the sixteenth, Great Britain declared that every European harbor from Brest to the mouth of the Elbe was blockaded. This was a distance of eight hundred miles, and even she had not ships enough to enforce her decree. Trafalgar had turned the heads of English statesmen.