Roman emperor Julian leaves Antioch with an army of 90,000 to attack the Sasanian Empire, in a campaign which would bring about his own death.

The Roman emperor was the ruler of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The title of imperator, originally a military honorific, was usually used alongside caesar, originally a cognomen. When a given Roman is described as becoming emperor in…