The Siege of Calais began in 1346, early in the Hundred Years' War (1337 to 1453). Edward III of England asserted dominion over France, and defeated the French navy in the Battle of Sluys in 1340. He went on to make raids throughout Normandy, the last of which led to the Battle of Crécy in 1346. By then, Edward's army in France required supplies and reinforcements from Flanders, so they withdrew to the north. English ships had already left Normandy for England. Edward needed a defensible port where his army could regroup and be resupplied.