[b] Jovian was born at Singidunum, Moesia Superior (today Belgrade in Serbia), in 331, son of Varronianus,[3] the commander of Constantius II's imperial bodyguards (comes domesticorum).

[5] Jovian accompanied the Emperor Julian on the Mesopotamian campaign of the same year against Shapur II, the Sassanid king.

[11] In exchange for an unhindered retreat to his own territory, he agreed to a thirty-year truce,[12] a withdrawal from the five Roman provinces, Arzamena, Moxoeona, Azbdicena, Rehimena and Corduena, and to allow the Sasanids to occupy the fortresses of Nisibis, Castra Maurorum and Singara.

[16] Faced with offensive graffiti and insulting authorless bills (famosi) throughout the city,[17] he ordered the Library of Antioch to be burned down.

[20] While en route from there to Constantinople, Jovian was found dead in his tent at Dadastana, halfway between Ancyra and Nicaea,[21] on 17 February 364.

[e] His death, which went uninvestigated,[19] was possibly the result of suffocating on poisonous fumes seeping from the newly painted bedchamber walls by a brazier.

[32] The Semi-Arian bishops received a poor greeting, while Athanasius delivered a letter to Jovian insisting on the Nicene Creed and the rejection of Arianism.

[34] By September 363, Jovian restored the labarum ("Chi-Rho") as the army's standard[28] and revoked the edicts of Julian against Christians, but did not close any pagan temples.

[35][i] He issued an edict of toleration, to the effect that his subjects could enjoy full liberty of conscience,[35] but he banned magic and divination.