The Earls of Northumbria [Morcar] and Mercia [Edwin] were unaware that Harold Godwinson was marching from the south to assist, and probably did not expect him to do so. They drew up their forces to block Hadraada and the Norsemen's way to York at a narrow point between the river Ouse and a marshy area south of the city. A fierce battle ensued lasting most of the day. The Norsemen eventually won by swinging their right wing to roll up the defenders. The Saxon Northern army lost a very large number of men, with the Norse army retiring east to Stamford Bridge to await tribute.