The Duke of Normandy was firmly resolved to assert his baseless claim to the throne by force of arms. He had a large treasure and many bold vassals, but he knew that his own strength was insufficient for such an enterprise as the invasion of England. Accordingly, he proclaimed his purpose all over Western Europe, and offered lands and spoil in England to every adventurer who would take arms in his cause. William's military reputation was so great, that he was able to enlist thousands of mercenaries from France, Brittany, Flanders, and Aquitaine. Of the great army that he mustered at the port of St. Valery, only one-third were native Normans. William took six months for his preparation; he had to build a fleet, since Harold had a navy able to keep the Channel, and to beat up every freelance that could be hired to take service with him. Nor did he neglect to add spiritual weapons to temporal: he won over the Pope to give his blessing on the invasion of England, because Harold had broken the oath he swore on the bones of all the saints, and had become a perjurer. There were other reasons for Pope Alexander's dislike for the English. Stigand, Harold's Archbishop of Canterbury, had acknowledged an anti-Pope, and Rome never forgave schism; moreover, the house of Godwine had not been friendly to the monks, but had been patrons of Dunstan's old foes, the secular canons. Alexander therefore sent William his blessing, and a consecrated banner to be unfurled when he should land in England. Hearing of William's vast preparations, Harold arrayed a fleet to guard the narrow seas, and bade the fyrd of all England to be ready to muster on the Sussex coast. He was prepared to defend himself, and only wondered at the delay in his adversary's sailing, a delay which was caused by north-westerly winds, which kept the Normans storm-bound. [Sidenote: =Harald Hardrada invades Northumbria.=] Suddenly there came to Harold disastrous and unexpected news from the north. His exiled brother Tostig had chosen this moment to do him an ill turn. He had gone to the north, and persuaded Harald Hardrada, the King of Norway, to invade England. Hardrada was the greatest Viking that ever existed, the most celebrated adventurer by sea and land of his age. When Tostig offered him the plunder of England, he took ship with all his host and descended on Northumbria. Morcar, the young earl of that region, came out to meet him, with his brother Eadwine at his side. But Hardrada defeated them with fearful slaughter before the gates of York, and took the city. [Sidenote: =Harold marches northward.--Battle of Stamford Bridge.=] When Harold of England heard this news he was constrained to leave the south, and risk the chance of William's landing unopposed. He took with him his house-carles, the great band of his personal retainers, and marched in haste on York, picking up the levies of the midland shires on the way.