Subsequent events are described by historians such as Symeon of Durham, Asser and Æthelweard in accounts that vary only in detail. According to the "Historia Regum Anglorum", following the invasion of the Danes, the previous "dissension" between Osberht and Ælla "was allayed by divine counsel" and other Northumbrian nobles. Osberht and Ælla "having united their forces and formed an army, came to the city of York" on 21 March 867. A majority of the "shipmen" (Vikings) gave the impression of fleeing from the approaching Northumbrians. "The Christians, perceiving their flight and terror", attacked, but found that the Vikings "were the stronger party". Surrounded, the Northumbrians "fought upon each side with much ferocity" until both Osberht and Ælla were killed. The surviving Northumbrians "made peace with the Danes".