Battle of Sluys The Battle of Sluys ( ; ) , also called Battle of l ' Ecluse , was a sea battle fought on 24 June 1340 as one of the opening conflicts of the Hundred Years ' War between England and France . The encounter was during the reigns of Philip VI of France and Edward III of England , in front of the town of Newmarket or Sluis , ( French " Écluse " ) , on the inlet between West Flanders and Zeeland . During the battle Philip ' s navy was almost completely destroyed , giving the English fleet complete mastery over the channel . However by the end of Edward ' s reign the French had rebuilt their fleet and were to become a threat again . Background . When France ' s Charles IV the Fair died in 1328 leaving only daughters , the nearest male relative was Edward III of England . The French establishment decided they did not want the English king on the French throne , and chose Edward ' s cousin , Philip , Count of Valois , to be king of France instead . The English kings had become dukes of Aquitaine after Henry II of England married Eleanor of Aquitaine in 1152 , from which point the lands in Aquitaine were held in vassalage to the French crown . Edward III did not see himself as subordinate to Philip and was reluctant to be Philip ' s vassal . Philip confiscated the lands that Edward held in Aquitaine , on the grounds that Edward had breached his obligation as vassal , precipitating what became known as the Hundred Years ' War in 1337 . At the beginning of the war , the French had the advantage at sea . The vessels they had were ideal for swift passage across the Channel under sail or oars . Galley s had been used by the Mediterranean powers and were adopted for trade and combat by the French . The galleys could penetrate shallow harbours and were highly maneuverable and ideal for raiding or ship - to - ship combat . The huge fleet of the French , was supplemented by galleys from Genoa ( some sources maintain that Castillian vessels were also part of the complement ) as well as by various captured English ships including two of Edward ' s finest , the cogs " Christopher " and " Cog Edward " ( also known as " The Edward " ) . The French were able to disrupt English commercial shipping , principally the Gascon wine and the Flanders wool trades , as well as raiding the south and eastern coasts of England at will . The English did not at that time have a purpose built navy . What they did have was a merchant marine ship known as a cog . The cog had a deep - draught and round - hull that was driven by a single great sail set on a mast amidships . These ships were arrested from the merchant service and converted into warships by the addition of wooden ' castles ' at the bow and stern , and the erecting of crow ' s nest platforms at the masthead , from which archers could use bows or drop stones on to enemy craft alongside . The cogs were two or three hundred tons and well able to carry many fighting men . Their high freeboard made them superior to the oared vessels in close combat , particularly when they were fitted with the castles . The king by common law was supposed to pay for the ships that he impressed into service . Edward assembled a combined fleet at Orwell and set up his headquarters on the " Cog Thomas " . The " Thomas " set sail , with Edward on board , from the Orwell estuary on 22 June 1340 , and was in sight of the roadstead at Sluys by the afternoon of the following day . Edward anchored at Blankenberge and in the evening of 23 June 1340 sent ashore Sir Reginald Cobham , Sir John Chandos , and Sir Stephen Lambkin to reconnoitre the French fleet . They found that the enemy vessels were ranged in three compact lines and included the captured English prize , the great cog " Christopher " ; the ships were crammed together tightly and anchored at the entrance of the Zwin ( also : Zwyn ) channel . Size of the fleets . The payroll records for the English fleet have been lost , therefore historians have had to rely on the estimates of chroniclers to ascertain the size of the fleet . This has varied widely from 120 to 320 vessels . However it is believed that the English fleet that set sail from Orwell , would have numbered about 160 ships . The chronicler Thomas Walsingham stated that Edward received late reinforcements from the northern squadron led by Sir Robert Morley . Edward III , in a letter to his son Edward , the Black Prince ( written on board the " Cog Thomas " ) dated 28 June 1340 , put the size of the French fleet as 180 sail . However , contemporary French documents for the engagement still exist and these record their fleet size as 204 vessels . It was under the command of the Breton knight Hugues Quiéret , admiral for the king of France , and Nicolas Béhuchet , Constable . Part of the fleet consisted of Genoese galleys serving as mercenaries under the command of Pietro Barbavera . There are however no verifiable records of any ships from Castille in this engagement . The battle . The dispositions of the French were made in accordance with the usual medieval tactics of a fleet fighting on the defensive . Quiéret and Béhuchet formed their forces into three or four lines chained together , with a few of the largest stationed in front as outposts . Admiral Barbavera , the experienced commander of the Genoese fleet , was concerned about this . He realised that they would lack manoverability in their anchorage and be open to attack from the ship - based English archers . He therefore advised the French commander to put to sea . Béhuchet , who as Constable exercised general command , refused to leave the anchorage as Barbavera suggested . Edward ' s intentions were well known , he wished to sail up the Zwin to Bruges and land his army to support his invasion plans . It is believed that Béhuchet ' s intention was to bar Edward ' s way . The extant records report that Edward entered the roadstead at high tide on 24 June 1340 , and that after maneuvering his ships to windward , sailed his fleet with the sun behind them towards the French . However , as the English fleet approached the Zwin estuary from the north west , it would appear highly unlikely that the sun would have been behind them , as modern research reveals that high tide would have been at 11 : 23am on the 24 June . Edward sent his ships against the French fleet in units of three , two ships crammed with archers and one full of men - at - arms . The English ships with the archers would come alongside a French ship and rain arrows down on its decks , the men - at - arms would then board and take the vessel . The English archers , with their long bows , could accurately fire twenty arrows per minute at a range of up to , whereas the Genoese crossbowmen could only manage two . The battle was essentially a land battle at sea . The two opposing ships would be lashed together and the men - at - arms would then engage in hand - to - hand fighting . As the battle progressed Béhuchet ' s tactics proved disastrous for the French , as it allowed the English to attack their left flank while leaving the rest of the fleet paralyzed . In a letter to his son Edward said that the enemy made a noble defense " all that day and the night after " . Many French ships were successfully boarded and captured after fierce battles . Genoese crossbowmen also managed to successfully board and capture two English ships . Edward made no mention of any actual help given him by his Flemish allies , though he said they were willing ; the French claim that they joined after dark . They also asserted that the king was wounded by Béhuchet , but this is not certain , and there was no evidence other than a legendary one of a personal encounter between him and the French commander . Nevertheless it would not be improbable . It is a sure fact , though , that the King was wounded by either an arrow or a bolt during the battle . By the end of the battle , the French fleet had been broken with the loss of only two English ships captured , and the water was reported to be thick with blood and corpses . Aftermath . With the French navy decimated and with Edward winning success at other naval engagements , he became confident enough to dispense with a regular navy . He chose instead to overwork his mercantile marine by continually impressing the ships and neglecting to pay for them . The result was that Merchants were ruined and shipbuilding ceased . By the end of Edward ' s reign the French had revived their navy and were again able to dominate the channel and raid the south coast of England .