Norwegian invasion he rushed north, gathering forces as he went, and took the Norwegians by surprise, defeating them at the Battle of Stamford Bridge on 25 September. Harald Hardrada and Tostig were killed, and the Norwegians suffered such great losses that only 24 of the original 300 ships were required to carry away the survivors. The English victory came at great cost, as Harold's army was left in a battered and weakened state, and far from the south. William's preparations and landing William assembled a large invasion fleet and an army gathered from Normandy and the rest of France, including large contingents from Brittany and Flanders. He spent almost nine months on his preparations, as he had to construct a fleet from nothing. According to some Norman chronicles, he also secured diplomatic support, although the accuracy of the reports has been a matter of historical debate. The most famous claim is that Pope Alexander II gave a papal banner as a token of support, which only appears in William of Poitiers's account, and not in more contemporary narratives. In April 1066 Halley's Comet appeared in the sky, and was widely reported throughout Europe. Contemporary accounts connected the comet's appearance with the succession crisis in England. William mustered his forces at Saint-Valery-sur-Somme, and was ready to cross the English Channel by about 12 August. But the crossing was delayed, either because of unfavourable weather or to avoid being intercepted by the powerful English fleet. The Normans crossed to England a few days after Harold's victory over the Norwegians, following the dispersal of Harold's naval force, and landed at Pevensey in Sussex on 28 September. A few ships were blown off course and landed at Romney, where the Normans fought the local fyrd. After landing, William's forces built a wooden castle at Hastings, from which they raided the surrounding area. More fortifications were erected at Pevensey. Norman forces at Hastings The exact numbers and composition of William's force are unknown. A contemporary document claims that William had 776 ships, but this may be an inflated figure. Figures given by contemporary writers for the size of the army are highly exaggerated, varying from 14,000 to 150,000. Modern historians have offered a range of estimates for the size of William's forces: 7,000–8,000 men, 1,000–2,000 of them cavalry; 10,000–12,000 men; 10,000 men, 3,000 of them cavalry; or 7,500 men. The army consisted of cavalry, infantry,