Charlemagne was king of the Franks from 768 until his death. He expanded the Frankish kingdoms than to transform them into an empire that incorporated much of Western and Central Europe. He conquered Italy and was crowned Imperator Augustus by Pope Leo III on 25 December 800 in Rome.
This happened to the Byzantine Empire as protector of Christianity. Given the initial outrage of Constantinople in 812 an agreement between the two leaders was signed, and again there were two emperors in Europe, one in the East and one in the West.
Commonly it has been associated with his reign Carolingian Renaissance, a revival of Latin culture and art through the Carolingian Empire and led by the Catholic Church. Through his foreign conquests and internal reforms, Charlemagne laid the foundation of what would become Western Europe in the Middle Ages. In French, German and the Holy Roman Empire monarchies, he is appointed as Carlos I.