The storm on 12 September1066, which had caused damage to the English fleet and forced that of William the Bastard, Duke of Normandy into the port of St Valery allowed the fleet of the Norwegian king, Harald Hardrada to sail down the east coast of Scotland. In addition to his own Norwegians, battle hardened during their recent war in Denmark, he had Danes, Swedes, Irish Norse, Icelanders, Greenlanders, men from the Faeroes, Orkney, Mann, the north of Scotland, Cumberland and the sundry isles. The fleet was about 360 ships strong giving a possible force of 12,000 fighting men. After a couple of minor landings along the English coast, Harald sailed to Scarborough on the Northumbrian coast. On or around 15 September he landed and burned the town. The fleet then sailed down to the Humber River, which it reached on 18 September.  Sailing up the Humber, then up the river Ouse, the Vikings reached the village of Riccall where they beached the ships and made camp. They were about 19 km from York, which was the capital of Northumberland. For many years York had been the capital of an independent Viking state and Harald Hardrada may well have expected a warm welcome; Tosti, on the other hand, having been expelled as Earl of Northumberland and had many of his men killed in the city, would have been more circumspect. The next day, having donned their armour, the Vikings marched on York.

Outside the city Earl Morcar of Northumberland, his brother, Earl Edwin of Mercia, and Earl Waltheof of Northampton waited for him. With the three young and inexperienced earls were their Huscarls and such elements of the Fyrds of their shires as they has managed to assemble in the short time they had had since the invading fleet had been sighted.

Although outnumbered, the English had the advantage of terrain. The battleground they had chosen was a swampy meadow situated between the Ouse and the road the Vikings had been following from Riccall to York. The English army formed up in a line whose right flank was anchored on the eastern bank of the Ouse, then stretched across the Fulford meadows to the track, and finally to a ditch on the other side of the track. Here the ground was soft marsh, thus protecting their flank. The line was several ranks deep, with Huscarls in the front of the centre. Behind them, and supporting the flanks were the Thegns and ceorls of the Fyrd.

Hardrada lined up his army opposite the English. He put his best men in the centre of the line, where he was stationed, and on the left side of the line, where they stretched out to the eastern bank of the Ouse. This ground was considerably firmer than that on his right flank and would therefore enable him to use his best troops to the best advantage. He stationed his less experienced troops on the right flank, extending them to the point where the ground became too soggy to support a man's weight. He expected nothing more of his right flank than to hold their ground against the more experience English who were facing them. He unfurled his battle banner, Landwaster and waited for the English to advance.

The English came, and soon the Viking right flank began to crumble and they gave ground along the track. To counter this, Hardrada ordered his left flank to spread out toward the centre so that they could hold the left and as much of the centre as possible without weakening the shield wall too much. He then called on his personal hearth troops, who were gathered around him in the centre, and wheeled them to the right and struck the advancing English on their left flank.

Being struck so suddenly and unexpectedly by a force that was superior both in numbers and experience, the English left flank was quickly destroyed and dissolved into small groups who fought desperately as they were driven back, not toward their old line, but  toward the ditch and the bogs. The morale of Harald's right flank, now the pressure was off them, quickly revived and they joined the rout. Slowly and bloodily, the Vikings commenced to roll up the English army. Soon the English right, over by the Ouse, was bent backward. The entire English line then collapsed and the army fled in disorder.

Following the battle, York acknowledged the inevitable, and surrendered to Harald and Tosti. In exchange for not having the city subject to sack, the burghers had to supply food, transport and hostages. It is thought that it was also demanded that Northumberland supply, not only more supplies, but fighting men. There must have been a feeling of hostility, however as, to ensure that they would fulfil their commitments, Harald Hardrada demanded an additional 100 hostages.

The date and place for the delivery of the hostages was Sunday, 25 September, at Stamford Bridge.