Excerpts from Books and Wikipedia
"Cornwallis saw his danger and dug in at Yorktown on the York River in Virginia, where he waited to be rescued by the Royal Navy. However, the French admiral, the Comte de Grasse, who had brought a strong fleet from the Caribbean, was able to block Chesapeake Bay and prevent the British navy form reaching the Yorktown garrison." [Furtado: 1001 Days] "The Battle of Yorktown proceeded like a textbook European siege. The patriots were poorly tutored in this military science in which the veteran French engineers excelled, relegating Washington again to a secondary position." [Chernow: Washington, p. 413]