In the Middle Ages, the term universal power referred to the Holy Roman Emperor and the Pope. Both were struggling for the so-called dominium mundi, or world dominion, in terms of political and spiritual supremacy.
The universal powers continued into the early 19th century until the Napoleonic Wars. The reshaping of Europe meant the effective end of the Empire. Although the Papacy had its territorial limits confined to the Vatican, it retained its soft power in the contemporary world.
Dominium mundi is the idea of universal dominion developed in the Middle Ages. Inspired by the memory of the Roman Empire, dominium mundi implied the recognition of one supreme authority, which generated a prolonged political and spiritual struggle between imperial and ecclesiastical power. This struggle can be said to have begun with the Investiture Controversy, and was mainly embodied by the Holy Roman Empire and Catholic Church, which elevated the emperor and the Pope, respectively, to the status of supreme ruler.
The idea of universal dominion divided Italy into the warring faction of Guelphs and Ghibellines. Guelphs supported the Church, while the Ghibellines supported the Empire. After two hundred years of division during the 12th and 13th centuries, neither one of the powers had prevailed, due to their mutual dependency and the rise of the powerful and practically independent reigns of Church and the State. The idea of dominium mundi did not reappear in its original form, despite the fact that both universal powers subsisted.
Papal supremacy is the doctrine of the Catholic Church that the pope, by reason of his office as vicar of Christ, the visible source and foundation of the unity both of the bishops and of the whole company of the faithful, and as priest of the entire Catholic Church, has full, supreme, and universal power over the whole church, a power which he can always exercise unhindered: that, in brief, "the pope enjoys, by divine institution, supreme, full, immediate, and universal power in the care of souls."
The doctrine had the most significance in the relationship between the church and the temporal state, in matters such as ecclesiastic privileges, the actions of monarchs and even successions.