He is ignored by the Georgian historic tradition, but mentioned by the 4th-century historian of the Roman Empire, Ammianus Marcellinus.
Saurmag seems to have succeeded on the death of his paternal grandfather, Mirian III, the first Christian king of Iberia, in 361 and pursued pro-Roman policy.
The Sassanid intervention in the Caucasus eventually drew a Roman response and, later in 370, Roman Emperor Valens sent in the twelfth legions—about 12,000 men—under Terentius who restored Saurmag in the western provinces of Iberia adjoining Armenia and Lazica, while Aspacures' successor Mihrdat III was permitted to retain control of the northeastern part of the kingdom.
The deal was not recognized by Shapur, who regarded it as grounds for war, and resumed hostilities against Rome early in 371.
[1] By 378, however, the Gothic War had constrained Rome to abandon Sauromaces; his realm must have ceased to exist as Iberia passed, whole or nearly so, under the Sassanid suzerainty.