When his father Floris IV was killed at a tournament at Corbie, William was only seven years old. His uncles William and Otto (bishop of Utrecht) were his guardians until 1239.
With the help of Henry II of Brabant and the archbishop of Cologne, he was elected in 1247 as king of Germany after Emperor Frederick II was excommunicated. After a siege of five months, he took Aachen in 1248 from Frederick's followers. Only then could he be crowned as king. Many of the German princes recognized his claim only after his marriage to Elizabeth of Brunswick in 1252.
From 1254, he fought a number of wars against the Frisians. In a battle near Hoogwoud on January 28, 1256, his horse fell through the ice, and William was killed. His body was recovered 26 years later by his son Floris V, who was only 2 years old when he succeeded his father. William was buried in Middelburg.
|List of German Kings and Emperors||
Alfonso X of Castile