He waged offensive war against the Carolingian Empire with some success, but was murdered under murky circumstances before a major confrontation had taken place.

Various modern scholars have used later Scandinavian, Frankish and Irish sources in a speculative way to determine the names of some of his other sons: Olaf, Ragnar, Kettil.

The Gesta Hammaburgensis ecclesiae pontificum of Adam of Bremen considers Hemming and Gudfred to be "patruelis", paternal cousins, but this is a derivative work.

In 798, the Saxons were defeated by the Obodrites, a West Slavic people allied to the Frankish Emperor Charlemagne, at the Battle of Bornhöved (or Schwentine River).

Charlemagne established a camp at Hollenstedt at the Elbe and sent an errand to Gudfred, asking him to extradite some rebels who had taken refuge in the Danish kingdom.

Fearing an invasion by the Franks, who had conquered heathen Frisia over the previous 100 years and Old Saxony in 772 to 804, Gudfred resolved to attack the Obodrites in the old Saxon territories.

The Obodrite prince Drożko (lat: Thrasco, Thrasucon) was expelled from his land, and another chief called Godelaib was captured by trickery and hanged.

[7] Before returning to his kingdom, Gudfred destroyed the important port Reric by the Baltic coast, probably in the modern Blowatz municipality.

The merchants were forced to follow the Viking fleet to Sliesthorp where the king stayed for some time and drew up plans for the future.

Denmark's most important town, Sliesthorp or 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.

[10] In the next year 809, Gudfred informed Charlemagne via travelling merchants, that he was aware of the emperor's ire over the invasion, and wished to negotiate a political solution.

The Vikings forced the merchants and peasants to pay 100 pounds of silver as "tax", implying that the king claimed Northern Frisia as Danish territory.

[13] According to the contemporary historian Einhard, Gudfred "was stuck-up by such a vain hope that he claimed the lordship over all of Germany; also, he did not see Frisia and Saxony as anything else but his provinces".

[14] Hearing this, the incensed emperor gathered whatever troops he could and established a camp at the confluence of Aller and Weser, awaiting the next step by the Danish ruler.

[19] The Frankish annals only expressly state that Gudfred ruled in South Jutland, but there are some hints of a wider sphere of royal power in the early 9th century.

In 813 a rebellion against the current Danish kings broke out in Vestfold, suggesting temporary suzerainty over part of southern Norway.

Saxo Grammaticus mentions him under the name Gøtrik, but his information is drawn from Adam of Bremen's chronicle (c. 1075) in conjunction with an unrelated Geatish saga character.

According to Saxo, Gøtrik was followed on the throne by his son Olaf who strove to avenge his father and thereby involved Denmark in civil war.

[21] The genealogical poem Ynglingatal, the date of which is disputed, mentions a King Gudrød the Hunter of Vestfold, son of Halfdan the Mild and grandfather of Harald Fairhair of Norway, who was slain by the servant of his vengeful wife Åsa.