Answer
Church leaders, such as bishops and archbishops, had influential roles in medieval European monarchies and often served as advisers to a country’s king. The church also acted as a counter against monarchs who wanted absolute power, since there was one power the church had over them -- excommunication. An excommunicated king could face leadership challenges from both inside and outside his kingdom, without the condemnation of church leaders. A clear example of this is King John of England, who was excommunicated from the Catholic Church in the 13th century after a dispute with Pope Innocent III. After encountering numerous difficulties, including the threat of a papal-backed French invasion, John agreed to once again swear fealty to the pope.