Edward had planned to ship his army to Sluys, in Flemish Zeeland, in mid-April, but most English merchantmen, aware that they were unlikely to receive the payments they were entitled to, were refusing to muster. The departure date was repeatedly postponed. On 4 June the King’s Council decided to sail with what ships they had, even though they could only carry 600 men-at-arms. On 10 June the Council received news that the Great Army of the Sea had arrived at Sluys, the main port of Flanders, on the 8th with consternation. Quiéret and Béhuchet had cut English communications with the continent. As they blocked the roadstead a further 10 ships reinforced them, bringing the total French strength to 213 ships.[22]

An acrimonious meeting of the Council took place. John de Stratford, Archbishop of Canterbury, a senior adviser, insisted that putting to sea would risk the loss of the King and that the whole expedition should be cancelled. The men in charge of the shipping arrangements were personally abused by the king. Stratford stormed out of the Council. In a fury Edward declared that “Those who are afraid can stay at home”.[23] A string of instructions went out. Coastal defences were stripped. Peremptory orders were sent to royal officers to brook no excuses from tardy mariners. Edward personally harangued the shipowners of Yarmouth, the largest port in England. Meanwhile, the horses which had already been loaded were unloaded and the erstwhile transports were rapidly converted to warships by having forecastles, aftercastles and crow’s nests added. To general amazement a sizeable fleet had been assembled at the Orwell by 20 June.[24] The payroll records for the English fleet have been lost, so historians have relied on the estimates of chroniclers to ascertain the size of the fleet. 66 ships which sailed with it have been identified by name and it is believed that it totalled between 120 and 150 ships.[18][25][26] Edward’s lieutenants were the Earls of Northampton and Huntington.[27] The fleet set sail early 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 sent ashore Reginald Cobham, Sir John Chandos and Stephen Lambkin to reconnoitre the French fleet.[18][28]

Edward’s intentions were well known; he wished to sail up the Zwin to Bruges and land his army to support his hard-pressed allies.[18] When the English were sighted the French fleet organised itself in three lines across the 3-mile wide (5 km) estuary of the Zwin to bar Edward’s way to the port of Sluys.[18] The ships of each line were bound together with chains and ropes to prevent the passage of enemy ships, “like a line of castles”.[18][29] Several large ships were stationed in the front of the line, including the very large captured English prize the Christopher. This was a normal medieval tactic for a fleet fighting on the defensive. Barbavera, the experienced commander of the galleys, was concerned about this. He realised that they would lack manoeuvrability in their anchorage and be open to attack from the ship-based English archers. He advised the French commander to put to sea and gain the weather gage, so as to be able to attack the English while they were disembarking, or deter this by the threat of an attack. Béhuchet, who as constable exercised overall command, knew little of naval operations. He viewed Barbavera as a mere commoner and near pirate, and wishing to take no chances of the English slipping past, insisted on holding a position blocking the inlet.[19]

Battle[edit] a model of a 14th-century merchant ship, or cog converted for warfare
A model of a Medieval merchant cog, converted into a warship
Cobham reported back late that night on the state of the French fleet. The extant records report that Edward entered the roadstead at high tide the next day, 24 June, manoeuvring to be able to attack with the advantage of wind and tide and with the sun behind them. The traditional view is that the attack took place at 3:00 p.m.[30][b] According to naval historian Nicholas Harris Nicolas modern research reveals that high tide would have been at 11:23 a.m. on 24 June.[18][c] After nearly a day linked by chains and ropes, and with wind and rain working against them, the French ships were driven to the east of their starting positions and become entangled with each other. Béhuchet and Quiéret ordered the ships to be separated, although in the event this proved difficult, and the fleet attempted to move back to the west, against the wind and the tide. In this disorganised state they made contact with the English.[33]

Edward sent his ships against the French fleet in units of three, two ships full of archers flanking one full of men-at-arms. The English ships with the archers would approach a French ship and rain arrows down on its decks; the men-at-arms would then board and take the vessel.[18][34][35] The modern historians Jonathan Sumption and Robert Hardy separately state that the English archers, with their longbows, had a rate of fire two or three times greater than the French crossbowmen and significantly outranged them:[36] Hardy reckons that the longbows had an effective range of 300 yards (270 metres) compared with 200 yards (180 metres) for the crossbows.[37]

The battle resembled a land engagement at sea. Two opposing ships would be lashed together and the men-at-arms would then engage in hand-to-hand fighting while supporting troops poured in arrows or bolts. As the battle progressed Béhuchet’s tactic of chaining his ships together proved disastrous for the French, as it allowed the English to attack single ships or small groups of ships with overwhelming force while the rest of the French were immobilised.[35][38][39] The greater number of fighting men in the English ships, especially archers, also told. A London longbowman reported that the English arrows were “like hail in winter”.[40] Many French ships were boarded and captured after fierce fighting. Barbavera had refused to tie his highly manoeuvrable galleys in with the French ships and the Genoese managed to board and capture two English ships. As it became clear that the battle was going the way of the English their Flemish allies sallied from the nearby ports and fell upon the French rear. In a letter to his son, Edward said that the French “made a most noble defence all that day and the night after”.[41]

Late at night the French rear line attempted to break out. Apart from the galleys only 17 other French ships escaped.[26] The rest of the French fleet, 190 ships, was captured. Few, if any, prisoners were taken and the water was reported to be thick with blood and corpses. French losses were between 16,000 and 20,000 killed,[26][42] a high proportion of these by drowning, including both French commanders; they were captured and Béhuchet was hanged from the mast of his own ship, while Quiéret was beheaded, in vengeance for the massacre they had overseen at Arnemuiden two years earlier and their raids on the English coast. Frenchmen who managed to swim ashore were clubbed to death by Flemish spectators. Only four English knights were killed, along with an unknown but small number of other English combatants.[38][43] The English joked that if the fish in Sluys harbour could speak, it would be in French, from the feast of French bodies they had dined on.[44] For days the tides washed up bodies.[45] Edward was wounded in the thigh by either an arrow or a bolt.[43] Sumption summarises that “The French had suffered a naval catastrophe on a scale unequalled until modern times”.[45]