The Battle of Sandwich, also called the Battle of Dover took place on 24 August 1217 as part of the First Barons' War. A Plantagenet English fleet commanded by Hubert de Burgh attacked a Capetian French fleet led by Eustace the Monk and Robert of Courtenay off Sandwich, Kent. The English captured the French flagship and most of the supply vessels, forcing the rest of the French fleet to return to Calais.
The French fleet was attempting to bring supplies and reinforcements to Prince Louis, later King Louis VIII of France, whose French forces held London at that time. The English vessels attacked from windward, seizing Eustace's ship, making Robert and the knights prisoner and killing the rest of the crew. Eustace, a notorious pirate, was executed after being taken prisoner.