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.
Antoninus Pius
Antoninus was the last Roman Emperor recognised by the Indian Kingdoms. Raoul McLaughlin quotes Aurelius Victor as saying "The Indians, the Bactrians and the Hyrcanians all sent ambassadors to Antoninus. They had all heard about the spirit of justice held by this great emperor, justice that was heightened by his handsome and grave countenance, and his slim and vigorous figure." Due to the outbreak of the Antonine epidemic and wars against northern Germanic tribes, the reign of Marcus Aurelius was forced to alter the focus of foreign policies, and matters relating to the Far East were increasingly abandoned in favour of those directly concerning the Empire's survival.