It is believed that his elder brother Halfdan became earl of some rich market towns south of the river Eider occupying what became known as North Frisia. Refusing to pay tax to Godfred, Halfdan swore his allegiance to Charlemagne in 807 to get his protection. Charlemagne gave eastern Holstein to the Obodrites and in 804 a Frankish army penetrated as far as the Ejder River, Denmark's traditional boundary at the time. The Frankish invasion never materialized, but it caused Godfred to construct the first sections of the Danevirke which ran from the Schlien toward the west coast of Denmark by means of the Trende River. The wall was built with an earthen embankment topped by a wooden stockade and protected from the south by a deep ditch. Denmark's most important town, Hedeby which apparently already existed on the Schlien was expanded and garrisoned with Danish soldiers and the early sections of the wall were designed to protect it.
Then in 808 King Godfred forced the Obodrites to acknowledge him as their overlord. When they refused, he attacked Reric, modern Lübeck, burnt it down, killed Chief Drożko and ordered the merchants to resettle at Hedeby, which was being integrated into the Danevirke defensive line.
In 810 Godfrid led 200 ships to plunder the Frisian coast, and forced the merchants and peasant to pay 100 pounds of silver and claimed Northern Frisia as Danish territory. That same summer he was killed by one of his housecarls. According to Notker of St Gall, the bodyguard who murdered King Godfred was one of his own sons.
To protect the northern coast of the Frankish Empire, the emperor began paying Viking chieftains to protect sections of the coast from the Schlien east to the Weser River.