Comte de Grasse helped trap Cornwallis at Yorktown by commanding the French fleet in the Chesapeake Bay.
François Joseph Paul de Grasse arrived in the Chesapeake in late August 1781 with a French fleet from the West Indies. His ships prevented British naval forces from supplying or evacuating Cornwallis’s army. On September 5, de Grasse fought the Battle of the Chesapeake against a British fleet commanded by Thomas Graves; the British failed to break the French position.
The naval blockade allowed American and French troops to concentrate around Yorktown. French ships also transported troops and helped bring heavy artillery into position. Cornwallis surrendered on October 19, 1781, after the allied army completed its encirclement.
De Grasse is often confused with Rochambeau, who commanded French land forces alongside Washington, or Lafayette, who led American troops in Virginia. Their cooperation was essential, but de Grasse’s specific contribution was naval control of the Chesapeake, a decisive factor in the Yorktown campaign.