In 1039, William inherited Weimar after the death of his father, while his younger brother Otton was transferred to Orlamunde .
In 1042, William was appointed as the Palatine of Saxony and was in this position for about a year.
According to the Altaikh Annals , in 1046, after the death of Margrave Ekkehard II, the emperor handed over to Count Dedi II von Wettin , Wilhelm's stepfather, two of the three stamps that Ekkehard owned, but Meissen held [1] . The ownership transferred to the Lady included the Saxon East (Luzhitsky) mark , the territories of the former Merseburg and Zeits marks, which were previously part of the Meissen mark , as well as the Thuringian mark. Later, the emperor transferred Wilhelm IV the Meissen Margrave, and the Dedi ceded the stepson to the Thuringian mark.
After the death of Emperor Henry III of Black in 1056 , William was a loyal supporter of Agnes de Poitiers , regency with her young son, Henry IV . In 1060, Wilhelm, together with the bishop of Naumburg-Zeitz Eberhard, led a campaign against the rebel Bela , brother of the King of Hungary Andras I. Andras died in a battle near Wieselburg , and his German allies were defeated. Wilhelm, showing courage in the battle, was captured with Eberhard [2] . The son of Bela, Geza I , persuaded his father not only to free the Margrave, but also to woo him Sofia , the daughter of Bela. However, the marriage did not take place, as William fell ill and died on his way home in 1062 . William's possessions were succeeded by his brother Otton.