What Was the Battle of Sluys?
The Battle of Sluys was fought on the morning of 24 June 1340 in the roadstead of the Zwin, off the Flemish port of Sluys (now part of Vlissingen, in the Netherlands). The English fleet, personally commanded by Edward III, attacked a much larger French and Genoese fleet at anchor and destroyed it. The battle was the first major engagement of the Hundred Years’ War, and it gave England control of the English Channel for the rest of the war; the prospect of a French invasion of England, which had been a serious concern through the late 1330s, ended in a single morning.
The French fleet at anchor
By the spring of 1340 the French had spent more than a year assembling a fleet in the Zwin. The purpose was twofold: to cover an intended French invasion of southern England and to support an overland campaign by the count of Hainaut and the duke of Brabant. The fleet included the king’s own great ships, the Genoese galleys hired from the Republic of Genoa (one of the largest concentrations of Genoese naval power outside the Mediterranean), and a substantial number of smaller barges and busses requisitioned from the French and Flemish ports. Modern estimates of the French total cluster around 190–200 vessels; the contemporary figures of 400, in the Gesta Edwardi de Carnarvon and the French chronicle of the Grandes Chroniques, are rhetorical.
The fleet was anchored in three dense lines across the mouth of the Zwin, with the larger Genoese vessels in the first line and the barges in the rear. The admiral was the Norman baron Hugh Quiéret, an experienced naval captain; the intendant was the routier commander Nicolas Béhuchet, who had been appointed to organise the fleet on the model of the routier companies he had led in Brittany. The two men hated each other, and the command arrangements were dysfunctional from the start.
The English fleet
Edward III had been preparing a counter-fleet at Harwich and the Suffolk ports since the autumn of 1339. The English fleet was smaller — perhaps 120–150 ships — but was composed almost entirely of high-sided northern European cogs, with their characteristic forecastles and sterncastles raised three or four decks above the waterline. These ships were effectively floating archery platforms, designed to carry large numbers of English longbowmen and to dominate the deck of any vessel they engaged. The English fleet was personally commanded by the king, who sailed in the Thomas, and the effective tactical direction was provided by Robert Morley, the admiral of the north, and John Chandos, who would later be the seneschal of Aquitaine.
The English sailed from Harwich on 22 June, made the passage in two days, and approached the Zwin on the evening of 23 June. Edward anchored out of range and waited for daylight. Jean Le Bel, a canon of Liège and a former soldier, was present on one of the Flemish vessels and recorded the impression of the English from the French side: the long row of high cogs, the bright shields hung over the sides, the horns and trumpets, the appearance of a king who had not yet won a battle and meant to win this one.
The morning of the battle
The English attacked on the flood tide, sailing directly into the anchored French. The Genoese galleys in the first line were the most dangerous opponents, but they were also the most difficult to manoeuvre at anchor. The English cogs came alongside, the archers loosed volleys from the castles, and the grappling-irons and boarding planks were thrown. The battle was, in effect, a mêlée on a sea of anchored hulls. The chronicler Froissart, who had access to veterans’ accounts, gives the figure of 18,000 French killed; the modern consensus is closer to 4,000–6,000 of all ranks, but the destruction of the fleet was total. Quiéret was killed on his ship; Béhuchet was captured and hanged from the yardarm of his own vessel. The Genoese survivors rowed out of the Zwin and made for the open sea.
The English losses were light. Edward anchored off Sluys for two days, took on water, and then turned east to support the now-unemployed army of his allies in the siege of Tournai. The campaign of 1340 ended with a nine-month truce at the papal mediation of Benedict XII; the next six years of the war would be fought on French soil, and the Channel would remain English.
The strategic consequences
The battle decided the question of the Channel for the rest of the war. Froissart, who was a partisan of the English cause, calls the engagement the greatest sea-battle in the history of Christendom. The judgment is generous, but the strategic fact is plain: without naval supremacy, Edward could not have landed at Saint-Mahon in 1346, could not have sustained a chevauchée through Normandy, and could not have resupplied the garrisons of Aquitaine through the long Caroline phase. Sluys was the necessary precondition of Crécy.
The political consequences were also immediate. Philip VI of France withdrew from the campaign, the count of Hainaut went home, and the German allies of Edward, who had been waiting for the French invasion to materialise, signed separate truces. The balance of advantage in the Low Countries, which had been finely poised in 1339, tipped decisively to the English.
The historiography
The English sources — the Gesta Edwardi de Carnarvon attributed to the chancery of Edward III, the Chronicon Henrici Knighton, and the longer prose Brut — give a unified, somewhat triumphal account. The French side, in the Grandes Chroniques and in the Norman and Parisian chronicles, is fragmented. The most useful single account remains Jean Le Bel’s, written within a decade of the event, and Froissart’s expansion of it a generation later. Jonathan Sumption’s first volume devotes a long section to the engagement; Clifford Rogers’ War Cruel and Sharp (2014) sets it in the larger strategic context of the Edwardian war effort. The site treats the Battle of Sluys within the larger Edwardian phase and within the naval history of the war.