Background
He was the fifth son of John I and Mary of Artois.
He was the fifth son of John I and Mary of Artois.
Because his four elder brothers all died childless between 1333 and 1337, he still became Marquis of Namur. William participated in the Hundred Years" War on the side of the English. Despite this, Namur itself remained at peace, except for a revolt of the weavers in 1351.
He was defeated and taken prisoner in the Battle of Baesweiler in 1371.
In 1362 he obtained from Charles IV, Holy Roman Emperor that Namur depended directly from the Holy Roman Empire and ceased to be a vassal of the County of Hainaut. He also developed the mining and forging industries, as well as commerce.