Europe entered a period which saw almost continuous war for the next century. Fighting took place in the Duchy of Brittany, "a country well suited to guerilla warfare", from 1342 to 1365 in the Breton War of Succession. The Hundred Years' War (1337–1453) between France and England continued, and Edward III led an invasion resulting in a number of victories. One of the earlier English victories was at the naval Battle of Sluys in 1340, which annihilated the French fleet and gave the English control of the English Channel for several years. The initial campaigns were frustrating and expensive, so Edward altered his strategy to use English armies that were lightly supported but prepared to forage off the land. It successfully established English control over Brittany in 1342. Further armies were sent to Brittany and Gascony in 1345, and Edward himself crossed the Channel in 1346 with 10,000 men — an enormous army by contemporary standards. They plundered Caen, an important town in Normandy, and eventually began moving back toward the Channel.