Fortified by the good news from De Grasse, Washington had an interview with De Rochambeau, and effected a junction with the French army. Thus strengthened, he opened his campaign against Cornwallis by beginning a movement against Clinton. The troops were massed above the city, and an effort was made to surprise the upper posts and destroy Delancey's partisan corps. The attempt, although well planned, failed of its immediate purpose, giving Washington opportunity only for an effective reconnoissance of the enemy's positions. But the move was perfectly successful in its real and indirect object. Clinton was alarmed. He began to write to Cornwallis that troops should be returned to New York, and he gave up absolutely the idea of sending more men to Virginia. Having thus convinced Clinton that New York was menaced, Washington then set to work to familiarize skillfully the minds of his allies and of Congress with the idea of a southern campaign. With this end in view, he wrote on August 2 that, if more troops arrived from Virginia, New York would be impracticable, and that the next point was the south. The only contingency, as he set forth, was the all-important one of obtaining naval superiority. August 15 this essential condition gave promise of fulfillment, for on that day definite news arrived that De Grasse with his fleet was on his way to the Chesapeake. Without a moment's hesitation, Washington began to move, and at the same time he sent an urgent letter to the New England governors, demanding troops with an earnestness which he had never surpassed. In Virginia, meanwhile, during these long midsummer days, while Washington was waiting and planning, Cornwallis had been going up and down, harrying, burning, and plundering. His cavalry had scattered the legislature, and driven Governor Jefferson in headlong flight over the hills, while property to the value of more than three millions had been destroyed. Lafayette, sent by Washington to maintain the American cause, had been too weak to act decisively, but he had been true to his general's teaching, and, refusing battle, had hung upon the flanks of the British and harassed and checked them. Joined by Wayne, he had fought an unsuccessful engagement at Green Springs, but brought off his army, and with steady pertinacity followed the enemy to the coast, gathering strength as he moved. Now, when all was at last ready, Washington began to draw his net about Cornwallis, whom he had been keenly watching during the victorious marauding of the summer. On the news of the coming of the French fleet, he wrote to Lafayette to be prepared to join him when he reached Virginia, to retain Wayne, who intended to join Greene, and to stop Cornwallis at all hazards, if he attempted to go southward.