Battle of the Chesapeake - Wikipedia

On September 5, 1781, during the Battle of Virginia Capes, French defeat British, and trap Cornwallis. From the article:

Admiral de Grasse had the option to attack British forces in either New York or Virginia; he opted for Virginia, arriving at the Chesapeake at the end of August. Admiral Graves learned that de Grasse had sailed from the West Indies for North America and that French Admiral de Barras had also sailed from Newport, Rhode Island. He concluded that they were going to join forces at the Chesapeake. He sailed south from Sandy Hook, New Jersey, outside New York harbour, with 19 ships of the line and arrived at the mouth of the Chesapeake early on 5 September to see de Grasse's fleet already at anchor in the bay. De Grasse hastily prepared most of his fleet for battle—24 ships of the line—and sailed out to meet him. The two-hour engagement took place after hours of maneuvering. The lines of the two fleets did not completely meet; only the forward and center sections fully engaged. The battle was consequently fairly evenly matched, although the British suffered more casualties and ship damage, and it broke off when the sun set. The British tactics have been a subject of debate ever since.

The two fleets sailed within view of each other for several days, but de Grasse preferred to lure the British away from the bay where de Barras was expected to arrive carrying vital siege equipment. He broke away from the British on 13 September and returned to the Chesapeake, where de Barras had since arrived. Graves returned to New York to organize a larger relief effort; this did not sail until 19 October, two days after Cornwallis surrendered.

'[The] Battle of the Chesapeake was a tactical victory for the French by no clearcut margin, but it was a strategic victory for the French and Americans that sealed the principal outcome of the war.'
— Russell Weigley"