Battle of Cassel (1071)

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Battle of Cassel
date February 22, 1071
place near Cassel, France
output Victory of Robert the Friesian
consequences Robert the Friesian takes over the county of Flanders
Parties to the conflict

Flemings and Frisians

Flemings, Normans and French


Robert the Frisian

Richilde vom Hennegau
Arnulf III. of Flanders
William FitzOsbern
Philip I of France
Eustach II of Boulogne

The Battle of Cassel was a military clash in medieval France that decided a power struggle in the county of Flanders . It took place on February 22, 1071 near Cassel .

Count Baldwin VI died in 1070 . of Flanders , whereupon his underage son Arnulf III. followed, for whom his mother Richilde von Hennegau took over the guardianship. The rule of the Hainaut was unpopular among the Flemish vassals , and her brother-in-law Robert the Friesian , who ruled in Holland, took the opportunity and invaded Flanders that same year. He quickly captured Bruges and Ghent , but was then captured by Count Eustach II of Boulogne . Around the same time, Richilde was also captured by Robert's followers, who were released in a prisoner exchange.

Richilde, whose followers were mainly concentrated in the south of Flanders, successfully requested military support from King Philip I of France, the overlord of Flanders. She also received support from her sister-in-law Mathilde , Robert's sister and wife of Wilhelm the Conqueror , even if William FitzOsbern, who was sent by her , moved to Flanders with only ten Norman knights. Shortly before the battle, King Philip I brokered a marriage between Richilde and William FitzOsbern in order to protect him as the protector of the young Count Arnulf III. to win.

In the battle of February 22, 1071, Robert the Frisian got the upper hand. William FitzOsbern fell in the fight as did Count Arnulf III. (called "the unfortunate"), who was slain by Gerbod the Flemish . Richilde and her second son, Baldwin , fled to their native Hainaut, which they were able to secure for themselves in the following years. But after the battle Robert the Frisian was the new Count of Flanders, which King Philip I, who fled to Montreuil, had to acknowledge. In the same year, both concluded an alliance against the Normans, with which Richilde's chances of recovering Flanders were dashed.


  • Lamperti Hersfeldensis Annales , ed. by Oswald Holder-Egger in MGH SS rer. Germ. 38 (1894), pp. 135-143
  • Flandria Generosa , ed. by Ludwig C. Bethmann in MGH SS 9 (1851), p. 322
  • Annales Egmundani , ed. by Georg Heinrich Pertz in MGH SS 16 (1859), p. 447
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  • Gilbert of Mons, Chronicle of Hainaut , ed. by Laura Napran (2005), p. 6