The King owned a small number of ships, which he maintained just as he kept a number of knights in his pay to form his personal retinue on land. During peace he hired these ships out to merchants, and when he called them back for war service he took the crews that navigated them into his pay, and sent his fighting-men on board. But the King's ships were the least numerous element in the war fleet. Merchantmen were impressed for service from London and the other maritime towns and cities, the feudal levy providing the fighting complement. A third element in the fleet was obtained from the Cinque Ports. There were really seven, not five, of them--Dover, Hythe, Hastings, Winchelsea, Rye, Romney, and Sandwich. Under their charter they enjoyed valuable privileges, in return for which they were bound to provide, when the King called upon them, fifty-seven ships and twelve hundred men and boys for fifteen days at their own expense, and as long after as the King paid the necessary charges. The naming of so short a term of service shows that maritime operations were expected not to last long. It was, indeed, a difficult matter to keep a medieval fleet at sea, and the conditions that produced this state of things lasted far into the modern period. Small ships crowded with fighting-men had no room for any large store of provisions and water. When the first scanty supply was exhausted, unless they were in close touch with a friendly port, they had to be accompanied by a crowd of storeships, and as the best merchantmen would naturally have been impressed for the actual fighting, these would be small, inferior, and less seaworthy ships, and the fleet would have to pay as much attention to guarding its convoy as to operating against an enemy. No wonder that as a rule the most that could be attempted was a short voyage and a single stroke. It was in 1340 that King Edward III challenged the title of Philip of Valois to the crown of France, and by claiming it for himself began "the Hundred Years' War." Both sides to the quarrel began to collect fleets and armies, and both realized that the first struggle would be on the sea. It would be thus decided whether the war was to be fought out on French or on English ground. The French King collected ships from his ports and strengthened his fleet by hiring a number of large warships from Genoa, then one of the great maritime republics of the Mediterranean. The Genoese sailors knew the northern seas, for there were always some of their ships in the great trading fleet that passed up the Channel each spring, bringing the produce of the Mediterranean countries and the East to the northern ports of Europe, and returned in the late summer laden with the merchandise of the Hansa traders.