From around 550 AD two Anglian kingdoms emerged in Northumbria. To the north of the River Tyne, occupying present-day Northumberland, was Bernicia, with its capital at Bamborough, ruled by the House of Ida. To the south of the Tyne was Deira, with its capital at York. There was fierce fighting between the Anglians and the Celts, with seiges at Holy Island and battles in the sand. The Celts were pushed back towards the Irish Sea. The two kingdoms were joined in 588 AD as Northumbria. King Ęthelfrith waged a ruthless war on the Celts, forcing the Cymry tribe out of Cumberland. When they fled into Wales they took their name with them and gave Wales its "Welsh" name Cymru.