What was the North Sea Empire?

During "The Viking Age," Norsemen settled throughout England and soon rose to become rulers. In fact, a personal union between the Kingdoms of England, Denmark, and Norway was established for three decades.

Though this "North Sea Empire," built upon maritime foundations, did not last long, its echoes can be found in English and Scandinavian history today.

A personal union of Denmark, England, and Norway

The North Sea Empire – sometimes known as the Anglo-Scandinavian Empire – was a personal union of the Kingdoms of Denmark, England, and Norway first united under Sweyn Forkbeard in 1013 CE. It lasted approximately 30 years until the death of his son, Cnut the Great, whose death in 1035 CE mortally damaged the empire. It was divided into three kingdoms, of which Harthacnut would inherit the Danish crown and conquer England. His death, in 1042 CE, spelled the end for the rump of the once-mighty North Sea Empire.

What makes this empire relatively unique in medieval European history is that it was a thalassocracy -  a maritime empire. The only way of connecting these three kingdoms into an empire was by the sea. The vast North Sea was thus a maritime highway connecting England, Norway, and Denmark.

How was it established?

It was the Danish King Sweyn Forkbeard that founded the North Sea Empire. He had already ascended to the throne of Denmark in 986 CE through revolting against his father (who was also brilliantly named, they just don’t seem to name monarchs like this anymore…) Harald Bluetooth. Securing the Danish throne was not enough for Forkbeard, and his gaze drifted northward to Norway.

Harald had already established a Danish foothold in parts of Norway, and Sweyn extended this through the ruthless use of force and Machiavellian alliances with Norwegian earls and noblemen. Following a huge naval battle, Svolder, Norway was thus split, and Forkbeard ruled most of coastal Norway personally or through vassalage.

Following the seizure of power in Norway, Forkbeard’s gaze turned across the North Sea to the British Isles. John of Wallingford, a Benedictine monk living in the mid-13th century, chronicles how Forkbeard raided England throughout the first decade of the 11th century CE. The massacre of Norsemen, in 1002 CE, upon the direct orders of the Anglo-Saxon King Æthelred the Unready, has been given as the prime motivation for Forkbeard’s raids and incursions into England.

By 1012 CE, however, after setbacks, including famine and the defection of a key warrior, Forkbeard invaded England. Marching on London, King Æthelred fled and sent his sons (including the last Anglo-Saxon King and future saint, Edward the Confessor) into exile. On Christmas Day, 1013 CE, Sweyn Forkbeard was crowned King of England but died five weeks later. His son, Cnut (Canute) the Great, would help cement his father’s maritime empire.

In 1015 CE, Cnut's huge Viking army invaded England to reclaim (what he thought was his rightful) crown. Photo: wolvie 74 / Pixabay

Cnut the Great: Solidifying the three thrones into one empire

The death of Sweyn Forkbeard did not fracture his precariously placed empire. Though he had two sons – one of which, Harald II, would succeed him as King of Denmark – it was the youngest, Cnut (Canute), that would solidify the North Sea Empire.

Upon the death of Forkbeard, the people living in the "Danelaw" (the Norse controlled areas of England) elected his son, Cnut, as King of England. However, not all would recognize their wish. The son of King Æthelred, Edmund Ironside, had been fortifying Anglo-Saxon resistance to the Norsemen and, through force, would become the de facto ruler of England.

It would take Cnut until 1015 CE to raise a huge Viking army and invade England to reclaim what he thought was his rightful crown. The next 14 months saw Cnut’s men trample, rape, and pillage huge swathes of southern England. Crossing the Thames in early 1016 CE, he then marched on London and, following a bloody siege, entered into negotiations with Edmund.

Cnut the Great was crowned King of England in 1017 CE – acknowledged by the peoples living in Danelaw and West Saxon areas.

It was just two years later that Cnut’s brother, Harald II, died, leaving the Danish throne up for grabs. Cnut then rushed across the North Sea to lay claim to the Danish throne. With all three thrones secure, thanks in part to his brilliant military nous, Cnut then had a successful reign of more than two decades.

Expansion and decline

Throughout the reign of Cnut, other areas and regions were brought into the North Sea Empire. He led a march into Scotland and made Malcolm II of Scotland his vassal. Furthermore, he also brought the Orkneys, Shetland, and Faroe islands under direct rule. Further alliances with Normandy and the Poles were made to secure his southern and eastern flanks. By the time of Cnut’s death, the North Sea Empire was the second largest and most important European political entity behind the Holy Roman Empire.

The empire fell apart more or less following Cnut’s death in 1035 CE. Norwegian noblemen brought the son of the murdered King Olaf to rule Norway. He would become King Mangus Olafsson. Further down south in Denmark, Cnut’s son, Harthacnut, had been proclaimed as King of Denmark and successor to Cnut at Nidaros Cathedral. He reunited the Danish and English crowns but could not retake the Norwegian throne. Following his death in 1040 CE, the last remnants of the North Sea Empire disappeared.

By this period, Scandinavia was becoming more and more Christianized, further integrating it into the political entities, empires, and intrigues of Europe. Alliances now would be made not between Scandinavia kingdoms but with the burgeoning Kingdoms of France, England, and the Holy Roman Empire.