Charlemagne, also known as Charles the Great or Charles I, was the King of the Franks from 768, the King of Italy from 774, the first Holy Roman Emperor, and the first emperor in western Europe since the collapse of the Western Roman Empire three centuries earlier. The oldest son of Pepin the Short and Bertrada of Laon, Charlemagne became king in 768 following the death of his father. He was initially co-ruler with his brother Carloman I. Carloman's sudden death in 771 under unexplained circumstances left Charlemagne as the undisputed ruler of the Frankish Kingdom. Through his military conquests, he subdued the Saxons and the Bavarians and pushed his frontier into Spain. He expanded his kingdom into an empire that incorporated much of Western and Central Europe. Charlemagne continued his father's policy towards the papacy and became its protector, removing the Lombards from power in Italy, and leading an incursion into Muslim Spain. He also campaigned against the peoples to his east, forcibly Christianizing them along the way, eventually subjecting them to his rule after a protracted war. Charlemagne reached the height of his power in 800 when he was crowned as "Emperor" by Pope Leo III on Christmas Day.