Irene of Athens
Charlemagne has been called the "Father of Europe" ("Pater Europae"), as he united most of Western Europe for the first time since the classical era of the Roman Empire and united parts of Europe that had never been under Frankish or Roman rule. His rule spurred the Carolingian Renaissance, a period of energetic cultural and intellectual activity within the Western Church. The Eastern Orthodox Church viewed Charlemagne less favourably due to his support of the filioque and the Pope's having preferred him as emperor over the Byzantine Empire's first female monarch, Irene of Athens. These and other disputes led to the eventual later split of Rome and Constantinople in the Great Schism of 1054.