Cornwallis forced his way into Virginia, joined Phillips’s troops, and established a supply base at Yorktown on the James River Peninsula. It turned out to be Washington’s great opportunity to make sure that Cornwallis would have no further campaigns. Taking advantage of French warships to blockade the Chesapeake Bay, Washington left a small force to keep an eye on Sir Henry Clinton in New York and trapped Cornwallis at Yorktown. Cornwallis surrendered after three weeks of siege.