William I served as

Bishop of Utrecht List of bishops and archbishops of the diocese and archdioceses of Utrecht. Medieval diocese from 695 to 1580 Founders of the Utrecht diocese * * * * * Bishops * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ...

from 1054 until his death in 1076. He was a typical representative of the German imperial system in which bishops (who couldn't inherit their lands) were the main officials of the empire. He was a loyal follower of king Henry IV of Germany. William was appointed when a war was going on against West Frisia (later part of the

county of Holland The County of Holland was a Imperial State, state of the Holy Roman Empire from its inception until 1433. From 1433 onward it was part of the Burgundian Netherlands, from 1482 part of the Habsburg Netherlands and from 1581 onward the leading pro ...

), which was resisting imperial authority. The imperial army conquered large parts of West Frisia in 1061, when Dirk V became count. King Henry gave the whole county to the bishopric of Utrecht in 1064. The whole of West Frisia was conquered in 1076 with the help of duke Godfrey III. William took part in the

Great German Pilgrimage of 1064–65 The Great German Pilgrimage of 1064–1065 was a large pilgrimage to Jerusalem which took place a generation before the First Crusade. Events It originated in the Kingdom of Germany in 1064, and was led by Archbishop Siegfried of Mainz, Bishop ...

. William supported the king during the

Investiture Controversy The Investiture Controversy or Investiture Contest (, , ) was a conflict between church and state in medieval Europe, the Church and the state in medieval Europe over the ability to choose and install bishops (investiture), abbots of monasteri ...

. He called for disobedience towards Gregory VII at the synod of Worms in 1076. Much of West Frisia was recovered by count Dirk after the death of bishop William in the same year.

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Further reading