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 and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The term emperor is a modern convention, and did not exist as such during the Empire. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Another title used was imperator, originally a military honorific, and caesar, originally a cognomen. Early emperors also used the title princeps alongside other Republican titles, notably consul and pontifex maximus.

Julian was the Caesar of the West from 355 to 360 and Roman emperor from 361 to 363, as well as a notable philosopher and author in Greek. His rejection of Christianity, and his promotion of Neoplatonic Hellenism and religious tolerance in its place, caused him to be remembered as Julian the Apostate in the Christian tradition.

Antioch on the Orontes was a Hellenistic Greek city founded by Seleucus I Nicator in 300 BC. One of the most important Greek cities of the Hellenistic period, it served as the capital of the Seleucid Empire and later as regional capital to both the Roman and Byzantine Empire. During the Crusades, Antioch served as the capital of the Principality of Antioch, one of four Crusader states that were founded in the Levant. Its inhabitants were known as Antiochenes. The remains of the ancient city of Antioch are mostly buried beneath alluvial deposits from the Orontes River. The modern city of Antakya, in Hatay Province of Turkey, lies in its place.