Rochambeau led his men to New York and joined the main American army. Washington now took command of the allied forces. He pretended that he was about to attack New York and deceived Clinton so completely that Clinton ordered Cornwallis to send some of his soldiers to New York. But the allies were marching southward through Philadelphia before Clinton realized what they were about. The French West India fleet under De Grasse reached one end of the Chesapeake Bay at the same time the allies reached the other end. The British fleet attacked it and was beaten off. There was now no hope for Cornwallis. No help could reach him by sea. The soldiers of the allies outnumbered him two to one. On October 17, 1781, four years to a day since the surrender of Burgoyne, a drummer boy appeared on the rampart of Yorktown and beat a parley. Two days later the British soldiers marched out to the good old British tune of "The world turned upside down," and laid down their arms.

This disaster put an end to British hopes of conquering America. But it was not until September, 1783, that Benjamin Franklin, John Adams, and John Jay brought the negotiations for peace to an end. Great Britain acknowledged the independence of the United States. The territory of the United States was defined as extending from the Great Lakes to the thirty-first parallel of latitude and from the Atlantic to the Mississippi. Spain had joined the United States and France in the war. Spanish soldiers had conquered Florida, and Spain kept Florida at the peace. In this way Spanish Florida and Louisiana surrounded the United States on the south and the west. British territory bounded the United States on the north and the northeast.