Clinton was in a constant state of apprehension, for he had good cause to fear the result of the attack that impended. Washington's plan, however, was changed, in the summer of 1781, by the news that a French fleet and a strong force would soon arrive in Chesapeake Bay and shut off Cornwallis from all assistance from Clinton. Washington decided to march southward and capture Yorktown and Cornwallis, meanwhile keeping Clinton under the belief that he meant to attack him. So well was the secret kept that Clinton's suspicions were not aroused until several days after the departure of the allied armies. De Grasse, the commander of the French fleet, arrived in Chesapeake Bay August 30th. Thus Cornwallis was blocked off from the sea, and enough soldiers were landed to prevent the British commander's escape by land. On the same day Washington and Rochambeau, after making a feint toward Staten Island, began a rapid march through New Jersey to Philadelphia, and thence to Elkton, Maryland. Officers and men were in high spirits, for they knew they were on the eve of great events. The citizens of Philadelphia shared the feeling, and cheered the men as they marched through the streets. On the way southward Washington made a hurried visit to Mount Vernon, which he had not seen since the opening of the war. Aware of the grave danger threatening Cornwallis, a British fleet made an effort to relieve him, but the more powerful French fleet easily beat it off. The allied armies boarded the waiting ships at Elkton, and, sailing down the Chesapeake to James River, joined Lafayette's force in front of Yorktown. [Illustration: THE SURRENDER AT YORKTOWN] The historical siege of Yorktown opened September 30, 1781. The French and American armies were ranged in a half-circle in front of Yorktown. Cornwallis was indignant at the apparent desertion by Clinton, and wrote to him in the middle of September: "This place is in no state of defense. If you cannot relieve me very soon, you must expect to hear the worst." Word came from Clinton that a fleet of twenty-three ships and more than 5,000 troops would sail to his relief about the 5th of October. The French soldiers in their gay uniforms and the Continentals in their rags maintained an ardent but friendly rivalry in pressing the siege. Washington aimed and applied the match to the first gun that was fired into Yorktown. Governor Nelson, being asked to direct the bombardment, selected the house which he believed to be the headquarters of Cornwallis, and calmly saw it battered to ruins. It was his own home.