In late summer of 1781, washington’s troops trapped cornwallis’s army at

I would not say, "late summer", because Siege of Yorktown initial movements started on September 28th and British troops surrender led by Lieutenant General Charles Cornwallis happened on October 19, 1781, at Yorktown, Virginia.  Franco-American commanders were General George Washington and Jean-Baptiste Donatien de Vimeur, Comte de Rochambeau. Siege of Yorktown was the last major land battle of the American Revolutionary War, as the surrender by Cornwallis, and the capture of his army, prompted the British government to negotiate an end to the conflict. After the British surrender, Washington sent Tench Tilghman to report the victory to Congress. The Treaty of Paris was signed on September 3, 1783, formally ending the war.