The St. Brice's Day massacre, known in Danish as "Danemordet" or "Massakren på Sankt Brictiusdag," took place on November 13, 1002, coinciding with the feast day of St. Brice, a fifth-century Bishop of Tours. This event occurred against a backdrop of escalating tensions and conflict between the Anglo-Saxons and Danes in England. After decades of relative peace, Danish raids on English territories resumed in the 980s, intensifying significantly in the early 990s. Following the Battle of Maldon in 991, King Æthelred the Unready began paying tribute, known as Danegeld, to the Danish king to prevent further attacks. Despite this, Danish raids continued, devastating Æthelred's kingdom annually from 997 to 1001, culminating in a Danish army rampaging across southern England in 1001, burning towns, and defeating Anglo-Saxon forces.
By 1002, King Æthelred had received information suggesting that the Danes in his kingdom intended to kill him, his councillors, and seize control of his kingdom. In response, Æthelred issued an order for the killing of all Danes in England. Although the decree seemed severe, historians generally believe that Æthelred's intention was not the wholesale extermination of all Danes but rather targeted recent Danish settlers, members of the invading army, and mercenaries who had betrayed him by joining the Danish invaders. While later chroniclers like William of Jumièges claimed the massacre targeted the entire Anglo-Danish population, modern historians believe this to be an exaggeration, with evidence suggesting that only Danish men in certain towns and regions were attacked. The historian Henry of Huntington noted that the killings were likely localized, and Ian Howard estimated that a few hundred Danes, mainly from the invading forces and their families, were killed.
One of the known victims of the massacre was Gunhilde, the sister of Sweyn Forkbeard, King of Denmark, along with her husband Pallig Tokesen, the Danish Ealdorman of Devonshire, who had participated in raids on the south coast. The killing of Gunhilde and other Danes enraged Sweyn Forkbeard, who launched a series of retaliatory wars against England. By 1014, these efforts culminated in the complete submission of England to Danish control. However, the union between Denmark and England proved unstable, and the link weakened after the reign of Sweyn’s son, Cnut the Great, eventually breaking apart during the reign of Cnut's son, Hardecanute. A final attempt to conquer England was made by the Norwegian king Harald Hardrada in 1066 but failed, ultimately paving the way for William the Conqueror's successful invasion later that year.