Why Was It A Mistake For Cornwallis To Retreat To The Yorktown Peninsula?

Why Was It A Mistake For Cornwallis To Retreat To The Yorktown Peninsula? Cornwallis was in Yorktown because he had been ordered by Clinton during the summer to provide a protected harbor for the British fleet in the lower Chesapeake Bay. Cornwallis chose Yorktown because of its deep-water harbor on the York River. Why was