Roman–Persian Wars: Emperor Julian arrives at Antioch with a Roman expeditionary force (60,000 men) and stays there for nine months to launch a campaign against the Persian Empire.

The Roman–Persian wars, also called the Roman–Iranian wars, took place between the Greco-Roman world and the Iranian world, beginning with the Roman Republic and the Parthian Empire in 54 BC and ending with the Byzantine and the Sasanian empires in 628 AD. While the conflict between the two civilizations did involve direct military engagements, a significant role was played by a plethora of vassal kingdoms and allied nomadic tribes, which served as buffer states or proxies for either side. Despite nearly seven centuries of hostility, the Roman–Persian wars had an entirely inconclusive outcome, as both the Byzantines and the Sasanians were attacked by the Rashidun Caliphate as part of the early Muslim conquests. The Rashidun offensives resulted in the collapse of the Sasanian Empire and largely confined the Byzantine Empire to Anatolia and southeastern Europe for the ensuing Arab–Byzantine wars.