Rodger also argues that for much of the fourteenth century, the French had the upper hand, apart from Sluys in 1340 and, perhaps, off Winchelsea in 1350. Yet, the French never invaded England and King John II of France died in captivity in England. There was a need for an English navy to play a role in this and to handle other matters, such as the insurrection of the Anglo-Irish lords and acts of piracy. By the early 1340s, it was clear that Edward's policy of alliances was too costly, and yielded too few results. The following years saw more direct involvement by English armies, including in the Breton War of Succession, but these interventions also proved fruitless at first. Edward defaulted on Florentine loans of 1,365,000 florins, resulting in the ruin of the lenders. A major change came in July 1346, when Edward staged a major offensive, sailing for Normandy with a force of 15,000 men. His army sacked the city of Caen, and marched across northern France, to meet up with English forces in Flanders. It was not Edward's initial intention to engage the French army, but at Crécy, just north of the Somme, he found favourable terrain and decided to fight a pursuing army led by Philip VI. On 26 August, the English army defeated a far larger French army in the Battle of Crécy. Shortly after this, on 17 October, an English army defeated and captured King David II of Scotland at the Battle of Neville's Cross. With his northern borders secured, Edward felt free to continue his major offensive against France, laying siege to the town of Calais. The operation was the greatest English venture of the Hundred Years' War, involving an army of 35,000 men. The siege started on 4 September 1346, and lasted until the town surrendered on 3 August 1347. After the fall of Calais, factors outside of Edward's control forced him to wind down the war effort. In 1348, the Black Death struck England with full force, killing a third or more of the country's population. This loss of manpower led to a shortage of farm labour, and a corresponding rise in wages. The great landowners struggled with the shortage of manpower and the resulting inflation in labour cost. To curb the rise in wages, the king and parliament responded with the Ordinance of Labourers in 1349, followed by the Statute of Labourers in 1351. These attempts to regulate wages could not succeed in the long run, but in the short term they were enforced with great vigour.