by Susan Flantzer
© Unofficial Royalty 2025

Cnut V was King of Denmark from 1146 to 1157, as co-king in shifting alliances with Sweyn III and Valdemar I. Born circa 1129, Cnut V was the son of Magnus (the Strong) Nielsen, the son of Niels I, King of Denmark, and Richeza of Poland.

On January 7, 1131, Cnut V’s father, Magnus the Strong, killed his cousin Cnut Lavard, Duke of Schleswig, the son of Eric I, King of Denmark, because he viewed Cnut Lavard as a rival to the Danish throne. The murder of Cnut Lavard started several years of civil war between King Niels and his son Magnus the Strong against Cnut Lavard’s illegitimate half-brother Eric Emune, the future Eric II, King of Denmark.

The civil war between the family members culminated on June 4, 1134, when the two sides fought the Battle of Fodevig near Lund in Scania, now in Sweden. The battle was a decisive victory for Eric Emune, who became the next King of Denmark as Eric II. Cnut V’s father, Magnus the Strong, was killed in battle, and his grandfather, King Niels, fled to Schleswig, where the citizens avenged Cnut Lavard, their beloved Duke of Schleswig, by murdering King Niels on June 25, 1134. Now a widow, Cnut V’s mother Richeza left her two sons in Denmark, returned to Poland, and married two more times.

In 1146, Eric III, King of Denmark became seriously ill and abdicated. Sweyn Grathe (Sweyn III), son of Eric II, King of Denmark, was elected King of Denmark by the nobles in Zealand, and Cnut Magnusson (Cnut V) was elected King of Denmark by the nobles in Jutland. For eleven years, there was a civil war, the Feud of 1146 – 1157, for the control of the Kingdom of Denmark, fought between King Sweyn III, King Cnut V, and King Valdemar I, the son of murdered Saint Cnut Lavard, Duke of Schleswig and the grandson of King Eric I of Denmark.

Cnut V traveled to Sweden to console his mother after the assassination of her third husband, Sverker I, King of Sweden. While in Sweden, Cnut V married a daughter of Sverker I from his first marriage, whose name is believed to be Helen.

Cnut V and Helen had four children:

In 1154, Cnut V joined with Valdemar I, and they were recognized as Co-Kings. In July 1157, Sweyn III, Cnut V, and Valdemar agreed to divide the Kingdom of Denmark between the three of them and serve as Co-Kings. This agreement barely lasted for a month.

The murder of Cnut V, King of Denmark at the Blood Feast of Roskilde; Credit – Wikipedia

On August 9, 1157, in what was supposed to be a reconciliation feast at Cnut V’s royal estate in Roskilde, Denmark, Sweyn III attempted to assassinate his rivals, Cnut V and Valdemar I. According to the Danish historian, theologian, and author Saxo Grammaticus (circa 1160 – after 1208), Sweyn III had planned the murder of his rivals and had his men carry out the attack. Cnut V, aged about twenty-eight, was killed, but Valdemar escaped, although he was wounded. This incident, known as the Blood Feast of Roskilde, is a significant historical event in Danish history. Cnut V’s burial site is unknown, but since he died in Roskilde, he may have been buried at Roskilde Cathedral.

Valdemar I defeated Sweyn III in the Battle of Grathe Heath on October 23, 1157. After the battle, while fleeing from the battlefield, Sweyn III was killed by a group of peasants. Having survived his rival pretenders to the Danish throne, Valdemar I became the sole King of Denmark, reigning until he died in 1182.

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Works Cited

• Autoren der Wikimedia-Projekte. (2007). Knut V Dänischer König. Wikipedia.org; Wikimedia Foundation, Inc. https://de.wikipedia.org/wiki/Knut_V._(D%C3%A4nemark)
• Bidragsydere til Wikimedia-projekter. (2006). Blodgildet i Roskilde. Wikipedia.org; Wikimedia Foundation, Inc. https://da.wikipedia.org/wiki/Blodgildet_i_Roskilde
• Bidragsydere til Wikimedia-projekter. (2003). Knud 5 Konge af Danmark (1129-1157). Wikipedia.org; Wikimedia Foundation, Inc. https://da.wikipedia.org/wiki/Knud_5.
• Flantzer, Susan. (2025). Niels, King of Denmark. Unofficial Royalty. https://www.unofficialroyalty.com/niels-king-of-denmark/
• Flantzer, Susan. (2025). Sweyn III, King of Denmark. Unofficial Royalty. https://www.unofficialroyalty.com/sweyn-iii-king-of-denmark/
• Wikipedia Contributors. (2024). Canute V of Denmark. Wikipedia; Wikimedia Foundation.
• Wikipedia Contributors. (2024). Helen of Sweden (12th century). Wikipedia; Wikimedia Foundation.