The Peace of Acilisene was a treaty between the Eastern Roman Empire under Theodosius I and the Sasanian Empire under Shapur III, which was resolved in 384 and again in 387.
The treaty, resolved in 384 and later in 387, divided Kingdom of Armenia between the Eastern Roman Empire and the Sasanian Empire. The Sassanids received the larger share called Persarmenia, while the Romans retained Sophene and a smaller portion of Armenia (called Lesser Armenia). This also created a new boundary line between the two empires, running from Erzurum to Mush.
Through this treaty, the Eastern Roman Empire admitted the loss of the Kingdom of Iberia to the Sasanians. During this period, Sassanian influence grew once again in eastern Georgia, and Zoroastrianism spread as far as Tbilisi, becoming "something like a second established religion of Iberia" until around mid-fifth century.