by Susan Flantzer
© Unofficial Royalty 2025
Illustration of Sweyn III in the 13th-century Saxon World Chronicle; Credit – Wikipedia
Born circa 1125, Sweyn III was a King of Denmark from 1146 to 1157, as co-king in shifting alliances with Sweyn III and Valdemar I. He was the illegitimate son of Erik II, King of Denmark and his concubine Thunna. Sweyn III’s father, Eric II, cruelly treated his enemies to secure and keep power. In 1137, when Sweyn III was about twelve years old, his father was killed at a thing, an assembly of nobles, in Umehoved, Denmark. A local nobleman, Sorte Plov (link in Danish), stabbed King Eric II with his spear in revenge for the execution of a relative.
Sweyn III was too young to become king, and his cousin Eric Haakonson reigned as Eric III, King of Denmark from 1137 – 1146. Eric III sent Sweyn III to the court of Konrad III, Duke of Franconia, in the Duchy of Franconia, located in present-day northern Bavaria, and parts of Hesse, Baden-Württemberg, and South Thuringia. There, Sweyn III became friends with Konrad III’s nephew, the young Friedrich of Swabia. Friedrich of Swabia was destined to become the powerful Friedrich Barbarossa, also known as Friedrich I, Holy Roman Emperor from 1155 until he died in 1190. Historians consider him one of the Holy Roman Empire’s greatest medieval emperors.
In 1146, King Eric III became seriously ill and abdicated. Sweyn III, about 21 years old, was elected King of Denmark by the nobles in Zealand, and Cnut Magnusson (King Cnut V), the son of Magnus the Strong and the grandson of King Niels I of Denmark, 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 Saint Cnut Lavard, Duke of Schleswig, and the grandson of King Eric I of Denmark.
In 1152, during the civil war, Sweyn III married Adela of Meissen (circa 1133 – 1181), the daughter of Conrad, Margrave of Meissen, and Luitgard of Ravenstein. They had two children:
In 1154, Valdemar I joined with Cnut V, 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-regents. This agreement barely lasted for a month.
The Blood Feast in Roskilde, created in 1250: Cnut V is killed and Valdemar is attacked, while Sweyn III follows with the royal crown; 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. 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 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.
King 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. According to local tradition, Sweyn III was buried where he was killed, and a chapel, later demolished, was built on the site. 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
- 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). Svend Grathe Konge af Danmark (1125-1157). Wikipedia.org; Wikimedia Foundation, Inc. https://da.wikipedia.org/wiki/Svend_Grathe
- Bidragsydere til Wikimedia-projekter. (2003). Valdemar den Store, Konge af Danmark (1131-1182). Wikipedia.org; Wikimedia Foundation, Inc. https://da.wikipedia.org/wiki/Valdemar_den_Store
- Flantzer, Susan. (2025). Eric II, King of Denmark [Review of Eric II, King of Denmark]. Unofficial Royalty. https://www.unofficialroyalty.com/eric-ii-king-of-denmark/
- Wikipedia Contributors. (2024). Canute V of Denmark. Wikipedia; Wikimedia Foundation.
- Wikipedia Contributors. (2024). Sweyn III of Denmark. Wikipedia; Wikimedia Foundation.
