On September 5, 1781, a French fleet under the Comte de Grasse defeated a British fleet under Admiral Thomas Graves off the Virginia Capes, in the engagement usually called the Battle of the Chesapeake. The fighting lasted about two hours. Neither side lost a ship.
That result was not indecisive. Cornwallis's army was at Yorktown, on the Chesapeake peninsula, waiting for the Royal Navy to bring supplies and take it off. De Grasse's squadron held the entrance to the bay, so when Graves withdrew to New York for repairs, Cornwallis was trapped. He was cut off. Washington had been marching south with the French army under Rochambeau since August, and the two forces closed on Yorktown within weeks.
Graves had twenty-four ships of the line against de Grasse's twenty-four, but the French squadron had brought extra crews from the West Indies, and the wind on the day let de Grasse hold the weather gage long enough to break through part of the British line. The tactical result was marginal and the strategic result was not.
He surrendered on October 19. The battle is the clearest example in the war of how a naval engagement fought by Europeans settled a campaign on the American mainland, decided at sea by ships that had sailed up from the Caribbean to be there on time.