Another leader from Ireland, one Sigtryggr, succeeded Rögnvaldr as king of Northumbria. He was on friendly terms with Aethelstan and married his sister in 925. He died in 926 or 927 and then Aethelstan took Northumbria under his own control. Sigtryggr's brother Guðröðr submitted to Aethelstan but after four days at the court of king Aethelstan 'he returned to piracy as a fish to the sea.' Both Sigtryggr and Guðröðr left sons bearing the name Anlaf (O.N. Ólafr) and with them Aethelstan and his successors had much trouble. Anlaf Sihtricsson lived in exile in Scotland and gradually organised against Aethelstan a great confederacy of Scots, Strathclyde Welsh and Vikings, both Danish and Norwegian, Anlaf Godfreyson brought help from Ireland and the great struggle began. The course of the campaign is uncertain but if the site of its main battle, 'Brunanburh,' is to be identified with Birrenswark Hill in S.E. Dumfriesshire, it would seem that Aethelstan carried the war into the enemy's country. The result of the battle was a complete victory for the forces of Aethelstan and his brother Edmund. Constantine's son, five kings and seven jarls were among the slain. We have in the Anglo-Saxon Chronicle a poem[6] celebrating the victory, and it describes in vivid language the hurried return home of Constantine, lamenting the death of his son, and the headlong flight of Anlaf Godfreyson to Dublin. England had been freed from its greatest danger since the days of king Alfred and his struggle with Guthrum. Aethelstan had no more trouble with the Norsemen and we have evidence from other sources that at some time during his reign, probably at an earlier date, he exchanged embassies with Harold Fairhair, king of Norway. The latter sent him a present of a ship with golden prow and purple sails and the usual bulwark of shields along the gunwale, while Harold's favourite son Hákon was brought up at Aethelstan's court. There he was baptised and educated and is known in Norse history as Hákon Aðalsteinsfóstri.