The Church had a close relationship with the English state throughout the Middle Ages. The bishops and major monastic leaders played an important part in national government, having key roles on the king's council. Bishops often oversaw towns and cities, managing local taxation and government. This frequently became untenable with the Viking incursions of the ninth century, and in locations such as Worcester the local bishops came to new accommodations with the local "ealdormen", exchanging some authority and revenue for assistance in defence. The early English church was racked with disagreement on doctrine, which was addressed by the Synod of Whitby in 664; some issues were resolved, but arguments between the archbishops of Canterbury and York as to which had primacy across Britain began shortly afterwards and continued throughout most of the medieval period.