 On September 6 , General Clinton wrote a letter to Cornwallis , telling him to expect reinforcements . Received by Cornwallis on September 14 , this letter may have been instrumental in the decision by Cornwallis to remain at Yorktown and not try to fight his way out , despite the urging of Banastre Tarleton to break out against the comparatively weak Lafayette . The British military leadership in New York held a council on September 17 in which they agreed that Cornwallis could not be reinforced until they had regained control of the Chesapeake . Historian Richard Ketchum describes the decision of the council as leaving Cornwallis " dangling in the wind . " One day earlier , Cornwallis wrote a desperate plea for help : " I am of the opinion that you can do me no effectual service but by coming directly to this place . " Before dispatching the letter on the 17th , Cornwallis added , " If you cannot relieve me very soon , you must prepare to hear the worst " . 
