In 696 he brought a contingent of spearmen to fight alongside King Aldfrith of Northumbria at the Battle of Loidis. The battle resulted in a decisive Northumbrian defeat, and Aldfrith was captured and taken hostage. Eadwulf, unwilling to waste any more of his men, abandoned Aldfrith's son Osred and retreated north to his own lands, allowing the south of the kingdom to be overrun by the victorious Britons.
Later that same year Osred Aldfrithson was defeated again and fled into exile in Frankia. Eadwulf saw an opportunity and had himself acclaimed king by his followers, restoring the independence of Bernicia. Over the next few years he successfully resisted several British incursions and crushed rebellions in Strathclyde and Rheged, ensuring the long-term survival of the English kingdom in the north.
Eadwulf died in 717 in battle against the Picts of Fortriu. He was succeeded by his son Earnwine .