later joined by other ships from Orkney. Threatened by Harold's fleet, Tostig moved north and raided in East Anglia and Lincolnshire. He was driven back to his ships by the brothers Edwin, Earl of Mercia and Morcar, Earl of Northumbria. Deserted by most of his followers, he withdrew to Scotland, where he spent the middle of the year recruiting fresh forces. Hardrada invaded northern England in early September, leading a fleet of more than 300 ships carrying perhaps 15,000 men. Hardrada's army was further augmented by the forces of Tostig, who supported the Norwegian king's bid for the throne. Advancing on York, the Norwegians occupied the city after defeating a northern English army under Edwin and Morcar on 20 September at the Battle of Fulford. English army and Harold's preparations The English army was organised along regional lines, with the fyrd, or local levy, serving under a local magnate – whether an earl, bishop, or sheriff. The fyrd was composed of men who owned their own land, and were equipped by their community to fulfil the king's demands for military forces. For every five hides, or units of land nominally capable of supporting one household, one man was supposed to serve. It appears that the hundred was the main organising unit for the fyrd. As a whole, England could furnish about 14,000 men for the fyrd, when it was called out. The fyrd usually served for two months, except in emergencies. It was rare for the whole national fyrd to be called out; between 1046 and 1065 it was only done three times, in 1051, 1052, and 1065. The king also had a group of personal armsmen, known as housecarls, who formed the backbone of the royal forces. Some earls also had their own forces of housecarls. Thegns, the local landowning elites, either fought with the royal housecarls or attached themselves to the forces of an earl or other magnate. The fyrd and the housecarls both fought on foot, with the major difference between them being the housecarls' superior armour. The English army does not appear to have had a significant number of archers. Harold had spent mid-1066 on the south coast with a large army and fleet waiting for William to invade. The bulk of his forces were militia who needed to harvest their crops, so on 8 September Harold dismissed the militia and the fleet. Learning of the