This was followed by another at the Battle of Confey (also known as the Battle of Cenn Fuait), against Augaire mac Ailella, overking of Leinster, who died in the battle. Augaire's death marked the end of effective opposition to the Vikings' return to Ireland. Sitric led his men on a triumphant return to Dublin, where he established himself as king, while Ragnall returned to England and soon became King of Northumbria. According to Downham, the departure of Ragnall and his contingent of warriors may have emboldened Niall Glúndub to try to expel the Uí Ímair from Ireland once again. In 919 Niall led a coalition of northern Irish kings south to Dublin. The forces of Sitric and Niall met near Islandbridge in modern-day County Dublin (dated 14 September by the "Annals of Ulster"). The resulting Battle of Islandbridge was an overwhelming victory for Sitric and his forces, with Niall falling in battle alongside one of his kinsmen. Five other kings, and a kinsman of the ruler of the Southern Uí Néill also died fighting against Sitric's army. In 920 the "Annals of Ulster" report that Sitric left Dublin "through the power of God". Sitric travelled to Northumbria where he assumed the kingship of Northumbria, succeeding his kinsman Ragnall who died the following year. Sitric was followed as King of Dublin by his brother or cousin Gofraid ua Ímair. In 920 Ragnall had submitted to Edward the Elder, King of the Anglo-Saxons. That same year, following his departure from Dublin, Sitric led a raid in Davenport, Cheshire, in violation of the terms of submission agreed between Ragnall and Edward. Smyth has suggested that this was an act of defiance by Sitric, indicating to Edward that he would not submit to him like Ragnall. Neither the "Anglo-Saxon Chronicle" nor Æthelweard's "Chronicon" makes mention of Sitric in the years 921–924, i.e. between his installation as King of Northubmria and the death of Edward the Elder. However, there are coins in existence which were minted at Lincoln during the period that bear Sitric's name. These are an important piece of evidence since they suggest Sitric ruled a large area south of the Humber, a claim contradicted by the "Anglo-Saxon Chronicle" which says that all the 'Danes' in Mercia (i.e. south of the Humber) submitted to Edward in 918.