History of the East–West Schism
Disunion in the Roman Empire further contributed to disunion in the Church. The Emperor Diocletian famously divided the administration of the eastern and western portions of the Empire in the early 4th century, though subsequent leaders (including Constantine) aspired to and sometimes gained control of both regions. Theodosius the Great, who established Nicene Christianity as the official religion of the Roman Empire (see Edict of Thessalonica), was the last Emperor to rule over a united Roman Empire. Following his death in 395, the division into western and eastern halves, each for a few decades still under its own Emperor, was never reunited.
House of Habsburg
After the death of his father in 1493, Maximilian was proclaimed the new King of the Romans, receiving the name Maximilian I. Maximilian was initially unable to travel to Rome to receive the Imperial title from the Pope, due to opposition from Venice and from the French who were occupying Milan, as well a refusal from the Pope due to enemy forces being present on his territory. In 1508, Maximilian proclaimed himself as the "chosen Emperor," and this was also recognized by the Pope due to changes in political alliances. This had a historical consequence in that, in the future, the Roman King would also automatically become Emperor, without needing the Pope's consent. In 1530, Emperor Charles V became the last person to be crowned as the Emperor by the Pope.