Battle of Dover (1217)
Coordinates: The Battle of Dover was a naval battle fought in early 1217 between an English fleet of 30-40 ships under Hubert de Burgh and a French fleet of 80 (mostly small craft) under Eustace the Monk. An English victory, the battle is notable as the first known example of the use of sailing tactics.
During the First Barons' War, the rebelling barons had asked Prince Louis take the throne of England away from King John. In 1216, Louis had landed in England and captured all of the Cinque Ports in the southeast, except for Dover, where de Burgh stubbornly held out against a siege of many months.
In August, Louis sent reinforcements for the siege across the English Channel, consisting of 900 troops and supplies on board 10 warships and 70 small craft. De Burgh had a fleet of 16 large ships and about 20 appropriated merchant vessels; he sailed out from Dover to intercept the French before they could land.
In a novel move, de Burgh attacked from upwind, first launching a shower of crossbow bolts, followed by quicklime dust to blind the French. After this, the ships closed for the usual boarding and hand-to-hand combat, in which the English were able to destroy or capture 3/4 of Eustace's ships.
Eustace was able to get away, but in the naval Battle of Sandwich in August, he was captured and beheaded.