Although the king maintained his own small flotilla, English fleets mostly consisted of requisitioned ‘impressed’ merchant vessels like the ones used at the Battle of Sluys. Edward III’s subordinates were empowered to requisition merchant vessels for their own use at any time. This was a feudal right, and Edward did not have to pay the owners. At the beginning of Edward III’s reign, trade was booming and there were a great many merchant ships operating in English waters. None of Edward III’s most likely adversaries could field a fleet anywhere near the same size. Scotland was an impoverished country which was less reliant on overseas trade, with few ports able to supply ships. In France, Philip VI’s authority was weak in many coastal areas. Gascony was an important wine trading area, but the province, which included the important naval town of Bayonne, was held by Philip’s most dangerous rival, the king of England. The dukes who controlled Brittany’s rugged, treacherous coastline intermittently intrigued with Edward III and were often overtly hostile. The main towns of Flanders were reliant on English wool and natural allies of England, despite the fact that their count was an enthusiastic supporter of the French king. The southern French coasts were remote from French royal authority. The local nobility sometimes intrigued with the king of Sicily or offered to hire ships to the English.

While the French could requisition ships from Normandy and Picardy, these were few in number, making the impact of the destruction at Sluys all the greater. Like the English admirals, French commanders were reliant on shipping surveys introduced under Richard I and King John to keep track of the ships available for arrest. A survey taken in 1336 showed that shipping was not plentiful in Normandy. Only thirty vessels were available for impressment in Le Havre, twenty-four in Dieppe, sixteen between Fecamp and Calais, and twenty-four in the rest of Normandy. That England was a more powerful maritime nation than France was well known. A contemporary French chronicler remarked that Edward III ‘always had a great fleet on the sea, [because] in truth he had more large ships than the king of France did’.