[4] When Julian departed from Constantinople in the spring of 362, his objective was clear: to launch a swift, decisive campaign against the Sasanian Empire rather than engage in a prolonged war.

[5][7] Procopius was tasked with coordinating Roman defensive efforts in the east, specifically working with King Arsaces II of Armenia to secure the strategically vital Bitlis Pass.

[6] Fearing Jovian's wrath, which had caused the death of another army candidate to the throne (Jovianus),[11] Procopius went into hiding, but later supervised the transport of Julian's body to Tarsus and its subsequent burial,[12] and only later went to Caesarea with his family.

[2] Becoming aware of discontent caused by the policies of Valens's praetorian prefect and father-in-law, Petronius,[15][16] Procopius decided to declare himself Emperor.

[18] He also emphasized his link to the Constantinian dynasty by appearing in public with Constantius II’s widow Faustina and their daughter Constantia, an act which Ammianus considered to have earned him greater support.

[19] Though Valens initially despaired of subduing the rebellion, and was inclined to come to terms with the usurper, he quickly rallied, guided by the counsels of Salutius and Arintheus, and the superior ability of his generals prevailed in two battles at Thyatira and Nacolia where Procopius's forces were defeated.

[20] He fled the battlefield, and was for a while a fugitive in the wilds of Phrygia, but was soon betrayed to Valens due to the treachery of his two generals Agilonius and Gomoarius, he was captured.