Pope Nicholas I, called Nicholas the Great, was the bishop of Rome and ruler of the Papal States from 24 April 858 until his death. He is remembered as a consolidator of papal authority, exerting decisive influence on the historical development of the papacy and its position among the Christian nations of Western Europe. Nicholas I asserted that the pope should have suzerainty over all Christians, even royalty, in matters of faith and morals.

Lothair II was the king of Lotharingia from 855 until his death in 869. He was the second son of Emperor Lothair I and Ermengarde of Tours. He was married to Teutberga, daughter of Boso the Elder.