The French and American armies united north of New York City during the summer of 1781. When word of de Grasse's decision arrived, both armies began moving south toward Virginia, engaging in tactics of deception to lead the British to believe a siege of New York was planned. De Grasse sailed from the West Indies and arrived at the Chesapeake Bay at the end of August, bringing additional troops and creating a naval blockade of Yorktown. He was transporting 500,000 silver pesos collected from the citizens of Havana, Cuba, to fund supplies for the siege and payroll for the Continental Army. While in Santo Domingo, de Grasse met with Francisco Saavedra de Sangronis, an agent of Carlos III of Spain. De Grasse had planned to leave several of his warships in Santo Domingo. Saavedra promised the assistance of the Spanish navy to protect the French merchant fleet, enabling de Grasse to sail north with all of his warships. In the beginning of September, he defeated a British fleet led by Sir Thomas Graves that came to relieve Cornwallis at the Battle of the Chesapeake. As a result of this victory, de Grasse blocked any reinforcement or escape by sea for Cornwallis and also disembarked the heavy siege guns required by the allied land forces. By late September, Washington and Rochambeau arrived, and the army and naval forces completely surrounded Cornwallis.