Edward struck first in 1340, he needed to secure control of the English Channel and won the battle of Sluys to do so. France’s navy consisted of a large number of galleys that were fast and could enter shallow harbours and were very manoeuvrable in close combat. They would prove a threat to English merchant vessels which at this time were largely engaged in the wool trade with Flanders and the wine trade with Aquitaine.
Sluys was located at the Zwin inlet between Flanders and Zeeland where much of the French navy some 200 ships were anchored compactly and chained together in three or four lines. Edward launched his fleet from the River Orwell and was planning to land an army in Bruges. Sources vary but a consensus suggests some 160 ships set sail many of these converted merchantmen. The French position barred him access to Bruges.
He assailed their position with groups of three ships, two crammed with archers and one with men-at-arms. His tactic was to turn a naval battle essentially into having the features of a land battle. They would pull alongside a French ship and the archers volleys would be followed by a boarding by the men-at-arms. English long bowmen could release twenty arrows a minute with great accuracy, the French/Genoese crossbowmen achieved just two a minute.
In this piece-by-piece approach the French fleet was broken, the Flemish joined in late in the day. The English lost just two ships and Edward was at some stage struck by an arrow or bolt. The French fleet was neutered.
A truce was agreed between the two nations until the summer of 1342.