Pope John XVIII was a major reformer and a stickler for making sure the clergy followed the rules of proper conduct. John flexed his Papal muscle during a dispute between three Bishops in France. Two Bishops refused to acknowledge Papal privileges given to the third and Pope John was not having this at all. He demanded an explanation and when the offending Bishops refused,he gave one of the most ballsy ultimatums in Church history. Either the Bishops settle their differences,or there would be no more more Church services in France. Period!(Holy Le Cow) The childish Bishops quickly backed down,on order of the King of France.
Pope John XVIII improved relations between Western and Eastern Churches,to the point of being revered in Constantinople. He is one of the few Popes to retire voluntarily and he lived out his last few years in a monastery.