King of Denmark (1104–1134), the last and longest-reigning son of Sweyn II, whose thirty-year rule ended in the civil war sparked by the murder of Canute Lavard.
Niels was king of Denmark from 1104 to 1134, the youngest and last of the five sons of Sweyn II to reign, and his was much the longest of their reigns. For most of three decades he presided over a relatively stable and peaceable kingdom, ruling with the counsel of the Church and the great magnates.
His reign ended in catastrophe. In 1131 his son Magnus murdered their popular kinsman Canute Lavard, Duke of Schleswig, igniting a civil war between the royal house and the friends of the murdered duke. Niels and Magnus were crushed at the Battle of Fotevik in 1134, Magnus was killed, and the old king, fleeing south, was cut down by the townsmen of Schleswig.
Niels was born about 1065, the youngest son of Sweyn II Estridsson, and came to the throne in 1104 after the death of his brother Eric I on pilgrimage. Four of his brothers had reigned before him; with Niels, the long succession of the sons of Sweyn reached its last and most durable king.
He married Margaret Fredkulla, a Swedish princess, whose influence lent his early reign a reputation for good order and reconciliation.
Niels is remembered as a mild, cautious, and somewhat colourless king, whose long reign owed more to careful management and the counsel of others than to any force of his own. For most of thirty years he kept the peace by working with the Church and the magnates rather than dominating them, and the sources treat this middle stretch of his rule as quietly successful.
His fatal flaw was in his family. Devoted to his son Magnus and anxious to secure the succession for him, Niels allowed — or failed to prevent — the murder of the beloved Canute Lavard, and then backed Magnus against the vengeance it provoked. The steady old king proved unable to master the forces that murder unleashed, and his reign, so long stable, collapsed in blood at its very end.
The peace of Niels's reign was shattered by dynastic jealousy. His nephew Canute Lavard — son of Eric Evergood, Duke of Schleswig, and a figure of great popularity and prestige — was seen as a rival to the succession of Niels's son Magnus. In 1131 Magnus lured Canute into a forest and killed him.
The murder outraged Denmark and brought Canute Lavard's half-brother, Eric, into open war against the king. The struggle culminated at the Battle of Fotevik in Scania in 1134, where Niels and Magnus suffered a crushing defeat.
Magnus was among the many killed at Fotevik. The aged Niels escaped the field and fled south, but at Schleswig — the city of the murdered Canute Lavard — the townsmen and the guild that had honoured the duke fell upon the king and killed him, on 25 June 1134. With him ended the reign of the sons of Sweyn.
Niels is remembered as the last of the sons of Sweyn and as the king whose long, stable reign ended in the dynastic murder that opened Denmark's age of civil wars. The killing of Canute Lavard, which he failed to prevent and then defended, set the royal house against itself for a generation. Out of that long conflict would rise Canute Lavard's own son, the future Valdemar I, who at last reunited the kingdom and founded the Valdemar dynasty.