Which emperor was killed in a campaign against the Persians in 363 A.D.?

Julian, often referred to as Julian the Apostate, was the emperor killed in a campaign against the Persians in 363 A.D. He was known for his attempts to revive paganism and to diminish the influence of Christianity in the Roman Empire. His campaign against Persia aimed to restore Roman prestige in the East after previous defeats. However, during this military endeavor, Julian suffered a fatal wound during the Battle of Samarra, leading to his death shortly thereafter.

The context of his reign is significant as he was the last non-Christian ruler of the Roman Empire, and his military strategies and philosophical ideas shaped subsequent discussions about the relationship of religion and state. His untimely death ended his reform efforts and had lasting implications for the religious landscape of the empire.