Sweyn Forkbeard, the son of Harald, mounts a series of wars of conquest against England in retaliation for the St. Brice's Day massacre of Danes in England.

By 1014, England has completely submitted to the Danes.

However, distance and a lack of common interests prevents a lasting union, and Harald's son Cnut the Great barely maintains the link between the two countries, which completely break up during the reign of his son Hardecanute.

A final attempt by the Norwegians under Harald Hardrada to reconquer England fails, but does pave the way for William the Conqueror's takeover in 1066.

Following the death of Canute the Great, Denmark and England are left divided and despite some attempts are never reunited.

Northwest Europe (964 – 1107 CE): Norman Conquest, Insular Kingdoms, and North Sea Networks

Geographic and Environmental Context

Northwest Europe includes Iceland, Ireland, the United Kingdom, the Faroe, Shetland, and Orkney Islands, the Channel Islands, and the western coastal zones of Norway and Denmark (west of 10°E).

• Anchors: London–York–Winchester, Dublin–Waterford–Cork, Bergen–Trondheim, Orkney–Shetland–Faroe–Iceland, Channel ports (Southampton, Dover).

Climate and Environmental Shifts

• Warm conditions supported population growth; herring shoals and cod grounds underpinned fisheries from North Sea to Iceland.

Societies and Political Developments

• England: consolidation under Anglo-Saxon kings (Æthelred II, Cnut the Great, 1016–1035, Edward the Confessor).

• Norman Conquest (1066): William seized England; castles, feudal estates, Domesday Book (1086).

• Ireland: Norse towns remained semi-autonomous; Irish high-kings (Brian Boru, d. 1014 at Clontarf).

• Scotland: Kings Malcolm II–III consolidated Lowlands; Norse jarls remained strong in Orkney/Hebrides.

• Norway/Denmark: Cnut’s North Sea Empire (England–Denmark–Norway); later Norway consolidated under Olaf Haraldsson (St. Olaf, d. 1030).

• Iceland: Christianization (c. 1000), Althing maintained self-rule under Norwegian overlordship by late 11th c.

Economy and Trade

• London grew as a major European port.

• Dublin, York thrived on slave trade, silver, and hides.

• North Sea commerce: wool, cloth, salt, fish; Norwegian timber and iron traded south.

• Flemish cloth towns (Ghent, Bruges, just across boundary in Atlantic West Europe) were key markets for English wool.

Belief and Symbolism

• Christianization of Scandinavia; churches founded across Norway, Denmark, and Iceland.

• Monastic expansion in England, Ireland, Scotland; Norman Romanesque architecture flourished.

Long-Term Significance

By 1107, the Norman monarchy dominated England; Scandinavia and Iceland were Christianized; the North Sea was a connected political and economic system.

Northwest Europe (1012–1023 CE): Danish Domination, Irish Struggles, and Regional Transformations

England: Danish Conquest under Sweyn and Cnut

The period from 1012 to 1023 CE marked a dramatic turning point in England’s history. Following years of Danish raids led by Sweyn Forkbeard, tensions exploded after King Æthelred the Unready ordered the St. Brice's Day massacre. In 1013 CE, Sweyn launched a decisive invasion, rapidly overcoming English resistance. Æthelred fled to Normandy, allowing Sweyn to become the first Danish king of England. Sweyn's sudden death in 1014 briefly returned Æthelred to power but brought further turmoil.

In midsummer 1015, Sweyn’s son Cnut (later known as Canute the Great) launched a powerful new invasion fleet, landing at Sandwich, Kent, virtually unopposed. Cnut's forces quickly moved through Wessex, ravaging Dorset, Wiltshire, and Somerset. Eadric Streona, the influential but notoriously unreliable alderman, initially assembled an English fleet but promptly submitted to Cnut. Unopposed, the Scandinavian army advanced into Mercia and plundered northward into Northumbria, where its ruler, Uhtred the Bold, was murdered. Subsequently, Northumbria was granted to Cnut’s ally, Eric Haakonsson, who had left Norway around 1014 or 1015 specifically to support Cnut’s campaign.

When Cnut's army turned south again toward London in early 1016, Æthelred died, and his son Edmund Ironside ascended to the throne. Edmund briefly rallied English resistance, but after several fierce battles and an inconclusive siege of London, he agreed with Cnut to divide the kingdom. Edmund’s death just months later cleared the path for Cnut, who became undisputed king of England in 1017. Cnut divided England into four territories: Wessex he retained for himself; East Anglia he gave to the Danish chieftain Thorkell the Tall; Northumbria went to Eric Haakonsson; and Mercia was returned to Eadric Streona—who was swiftly executed later that year for treachery. Cnut’s reign thus established a Danish-dominated North Sea empire that significantly reshaped the region.

Ireland: Brian Boru’s Last Years and the Battle of Clontarf

In Ireland, tensions grew following High King Brian Boru’s divorce from his formidable wife, Queen Gormflaith, in the early 1010s. Gormflaith subsequently began orchestrating opposition to Brian, fueling rising discontent among the Leinstermen. Relations with Leinster had deteriorated so sharply that by 1012, open rebellion erupted, challenging Brian’s rule.

This opposition climaxed dramatically at the Battle of Clontarf on April 23, 1014. Brian’s forces confronted a broad coalition of rebellious Leinstermen and their Norse allies from Dublin and overseas. Although Brian’s army achieved victory, dramatically weakening Norse influence in Ireland, Brian himself was slain during the battle. His death removed a unifying figure, plunging Ireland back into political fragmentation.

Scotland: Stability Under Malcolm II

In Scotland, Malcolm II (r. 1005–1034) continued to solidify central authority. Throughout this period, Malcolm expanded his territories, notably securing control over Lothian. This consolidation provided critical stability and reinforced Alba’s internal coherence amidst the broader instability in Britain and Ireland.

Iceland: Consolidation of Christian Institutions

Following Iceland’s peaceful adoption of Christianity (1000 CE), the Icelandic Commonwealth further integrated ecclesiastical institutions and Christian laws into daily governance. The peaceful religious transition allowed Iceland to develop closer cultural ties with the European mainland without sacrificing the autonomy of its unique parliamentary system, the Althing.

Norse Settlements: Maritime Networks and Cultural Stability

Communities in Orkney, Shetland, and the Hebrides remained economically prosperous and culturally distinctive during this period, even as Norse power declined in Ireland after Clontarf. These island settlements continued as important maritime hubs, balancing cultural influences from Scandinavia, Ireland, and Anglo-Saxon England.

Literary and Cultural Developments

Around 1000 CE, the compilation of the Irish Dindseanchas cataloged legendary sites on the Hill of Tara, reinforcing the symbolic cultural unity Brian Boru sought. Meanwhile, around 950–960 CE, the compilation of the Cædmon manuscript in England reflected continuing vibrant intellectual and literary traditions, despite the turbulent political backdrop.

Legacy of the Era

By 1023 CE, Northwest Europe had undergone profound transformations. Cnut’s consolidation of power in England established a durable Danish presence, dramatically reshaping political alliances and territorial administration. Brian Boru’s reign and subsequent death at Clontarf marked a pivotal point for Ireland, sparking renewed political fragmentation exacerbated by personal rivalries and rebellions, notably those incited by Gormflaith. Meanwhile, Malcolm II’s stable governance in Scotland contrasted sharply with instability elsewhere. Iceland’s embrace of Christianity strengthened its European cultural alignment while preserving political independence.

These complex interwoven events set critical precedents, laying the groundwork for continued change in Northwest Europe throughout the eleventh century.

Ireland’s High King Brian Boru divorces Queen Gormflaith some time during the 1010s, and she begins to engineer opposition to the High King.

Relations between Brian and Leinster have become so strained that revolt breaks out among the Leinstermen around 1012.

Eric Haakonsson leaves Norway in 1014 or 1015 and joins Cnut, later known as Canute the Great, for his campaign in England.

The Scandinavian invasion fleet lands at Sandwich in midsummer 1015 where it meets little resistance.

Cnut's forces move into Wessex and plunder in Dorset, Wiltshire and Somerset.

Alderman Eadric Streona assembles an English force of forty ships and submits to Cnut.

The Scandinavian army moves over the Thames in early 1016 into Mercia, plundering as it goes.

Prince Edmund attempts to muster an army to resist the invasion but his efforts are not successful.

Cnut's forces continue unhindered into Northumbria where Uhtred the Bold, earl of Northumbria, is murdered.

The great north English earldom is given by Cnut to Eric after he wins control of the North.

The invading army turns south again towards London.

King Æthelred the Unready dies before they arrive, and Prince Edmund is chosen king.

The Scandinavian forces besiege London.

After several battles, Cnut and Edmund reach an agreement to divide the kingdom, but Edmund dies a few months later.

Cnut, as the undisputed king of all England in 1017, divides the kingdom into four parts.

Wessex he keeps for himself, East Anglia he gives to Thorkell, Northumbria to Eric and Mercia to Eadric.

Cnut has Eadric executed as a traitor later in the same year.

Cnut, the first Viking chieftain welcomed by the church as an equal to Christian kings, establishes close ties with his fellow Vikings, the Normans.

Eventually embracing Christianity, he becomes a founder and patron of monasteries.

When, in the early tenth century, the relics of the martyred king, St Edmund, were translated from Hoxne to Beodricsworth, afterwards known as St. Edmundsbury, the site had already been in religious use for nearly three centuries.

To the small household of Benedictine monks who guard the shrine the surrounding lands are granted in 1020, during the reign of Cnut.

Monks are introduced from St Benet's Abbey under the auspices of the Bishop of Elmham and Dunwich.

Christianization has to some extent settled the Vikings.

The Danes, who, under Cnut the Great, have created a North Sea empire by reconquering England, swallow parts of Sweden and all of Norway in 1028, although the Norse Earldom of Orkney in Northern Scotland never really falls into the Danish sphere.

Northwest Europe (1024–1035 CE): Consolidation, Succession, and New Alliances

England: Consolidation Under Cnut the Great

From 1024–1035 CE, Cnut the Great (r. 1016–1035) firmly established his rule in England, bringing a period of unprecedented stability after years of turmoil. Cnut effectively combined Danish and English governance, marrying Æthelred the Unready’s widow, Emma of Normandy, which helped legitimize his claim and stabilize Anglo-Saxon acceptance of Danish rule. He carefully maintained balanced relationships between his realms in England, Denmark, and Norway, thus solidifying the "North Sea Empire."

In this decade, England benefited from peace, renewed trade, and the implementation of strong, centralized government. Cnut respected and adapted existing Anglo-Saxon administrative structures, issuing laws reflecting both Danish and English traditions, and successfully integrated Danish nobility into the English ruling class, facilitating cultural exchanges and reducing ethnic tensions.

Scotland: Malcolm II’s Continued Rule

In Scotland, Malcolm II (r. 1005–1034) maintained a stable and assertive reign, strengthening central royal authority. By 1031, he had secured recognition of Scottish overlordship over the kingdom of Strathclyde, decisively influencing Scotland’s territorial cohesion. Malcolm’s death in 1034 would lead to a complex succession, as he was succeeded by his grandson Duncan I, setting the stage for significant internal strife in subsequent decades.

Ireland: Fragmentation after Brian Boru’s Legacy

Following the death of Brian Boru (1014), Ireland remained politically fractured. Throughout 1024–1035, no singular high king emerged to replace Brian's dominance. Rather, Ireland was divided into competing regional kingdoms, notably Munster, Leinster, Connacht, and Ulster. Each pursued autonomy, often forming short-lived alliances or engaging in intermittent warfare. Despite instability, Ireland continued as a vital center of monastic scholarship and cultural vitality, preserving rich traditions and literary heritage.

Norway and Denmark: Cnut’s North Sea Empire

In 1028, Cnut expanded his authority to Norway, solidifying his North Sea Empire. He secured recognition as king of Norway after expelling the Norwegian king, Olaf Haraldsson (later known as Saint Olaf). This remarkable consolidation brought England, Denmark, and Norway under a single monarch, marking a pinnacle of Danish influence in Northwest Europe. Eric Haakonsson, Earl of Northumbria, remained a crucial ally and administrator in England and the northern territories until his death around 1024. Cnut’s vast empire fostered unprecedented cross-cultural contact and trade, shaping regional politics significantly.

Iceland and the Norse Atlantic Settlements: Stability and Cultural Growth

During 1024–1035, Iceland continued to benefit from stable governance under the Althing system and newly-established Christian institutions. Its religious transition facilitated deeper European connections, enhancing literary activities, including the growth of sagas and genealogical literature. Norse communities in the Faroes, Orkney, and Shetland remained stable, economically active, and culturally vibrant, maintaining significant autonomy and ongoing trade networks linking them closely with the North Sea Empire.

Intellectual and Religious Life

This period witnessed notable religious developments. The veneration of Saint Olaf Haraldsson, killed at the Battle of Stiklestad (1030) after attempting to regain Norway, quickly spread throughout Scandinavia and England, significantly influencing religious practices and pilgrimages. Olaf’s martyrdom and subsequent canonization greatly bolstered Christianization in Scandinavia, reinforcing cultural integration within Cnut’s domains.

In England, monastic communities flourished under stable royal patronage. Intellectual life continued to prosper through chronicles, such as continued entries in the Anglo-Saxon Chronicle, which recorded key contemporary events and offered valuable historical insights.

Succession Crisis after Cnut’s Death

The stability achieved by Cnut unraveled swiftly following his death in 1035. He was succeeded briefly by his sons Harold Harefoot and Harthacnut, whose rivalries and ineffective rule resulted in renewed uncertainty and eventual disintegration of the North Sea Empire. This succession crisis set the stage for England’s political instability and increased local tensions in the ensuing decades.

Legacy of the Era

By the close of 1035 CE, Northwest Europe had experienced remarkable political unification under Cnut’s North Sea Empire, alongside continuing fragmentation in Ireland and gradual stabilization in Scotland. Iceland and the Norse settlements thrived culturally and economically, bolstered by stable institutions and Christianization. The death of Cnut in 1035 marked a turning point, ushering in a new phase of fragmentation and power struggles that would reshape regional dynamics profoundly in subsequent decades.

King Cnut of England and Denmark seeks to restore Danish rights in Norway, lost in 1016 upon the ascension of native Olaf Haraldsson as monarch.

Olaf and King Anund Jacob of Sweden, seeing the combined Anglo-Danish kingdom as a threat—Cnut's father Sweyn had asserted power over both their countries—take advantage of Cnut's being in England to attack the Danes in the Baltic Sea in 1025 or 1026, and are joined by Ulf Jarl, Cnut's Danish regent, and his brother.

Ulf Jarl is the son of Thorgils Sprakalägg, who is claimed to have been the son of Styrbjörn the Strong, a scion of the Swedish royal house, by Tyra, the daughter of king Harald Bluetooth of Denmark.

However, Thorgils' parentage may have been invented to glorify the royal dynasty founded by Ulf's son, Sweyn Estridson.

Ulf had joined Cnut’s expedition to England.

He had married Cnut's sister Estrid in about 1015 and was appointed the Jarl of Denmark, which he rules when Cnut is absent.

He is also the foster-father of Cnut's son Harthacnut.

When the Swedish and Norwegian kings attack Denmark, Ulf persuades the freemen, who are discontent at Cnut's absentee rule, to elect Harthacnut king.

This is a ruse on Ulf's part, as his role as Harthacnut's guardian will make him the ruler of Denmark.

When Cnut learns what has happened, he returns to Denmark and confronts his enemies at the Battle of the Helgeå, where the Swedish and the Norwegian navies led by kings Anund Jacob and Olaf II lie in wait up a river for the navy of King Cnut, which is commanded by Ulf Jarl.

Cnut's navy is massive and his own ship is said to have been eighty meters long.

The Swedish and the Norwegian kings had ordered a large dam made of peat and lumber to built on the river.

When the Danish navy sails in, the water is released and a great many Danes and Englishmen drown in the deluge.

However, Cnut's men are apparently able to win the battle.

The outcome is disputed, but Cnut comes out best; Olaf flees and the threat to Denmark is dispelled.

The apparent victory leaves Cnut as the dominant leader in Scandinavia.

The battle is retold in skaldic poetry and in sources such as the Danish Gesta Danorum by Saxo Grammaticus and the Icelandic Saga of Olaf the Holy by Snorri Sturluson.

Opinions are divided on whether the location was at Helgeå in Uppland or the Helgeå of eastern Skåne.

In the Anglo-Saxon Chronicle, the battle is dated to 1025 and the Swedes won the battle.

Cnut claims to rule "part of Sweden" together with England, Denmark, and Norway.

At some time after the Battle of the Helgeå, he subjugates the core provinces of Sweden around Lake Mälaren, where he has his own coins minted either in the capital, Sigtuna, or in Lund, at this time part of Denmark, with the inscription CNVT REX SW ("Cnut King of the Swedes").

Western Götaland or Blekinge have been suggested.

It is probably an overlordship more than actual rule; Cnut does not have to be present in Sweden to order the minting of coins.

Coins are also minted asserting he rules Ireland, and Swedish history at this early date is so uncertain that we can hardly be sure even of the names of the kings.

Denmark is threatened by Norway and Sweden in the 1020s, and Cnut decides in 1026 to strengthen its defenses by bringing over his eight-year-old son to be the future king under a council headed by his brother-in-law, Earl Ulf.

However, Ulf alienates Cnut by getting the Danish provinces to acknowledge Harthacnut as king without reference to Cnut's overall authority and by failing to take vigorous measures to meet Norwegian and Swedish invasions, instead waiting for Cnut's assistance.