Western Armenia
In 387, from the Sasanian invasions of Armenia, led the Roman emperor Theodosius I and the Sasanian King Shapur III to negotiate into a treaty called the Peace of Acilisene. This led the whole Roman Client Armenian Kingdom to be partitioned into two empires: Western Armenia to be under Roman rule and Eastern Armenia to be under Sasanian rule. Later in 387, the last Roman Client Armenian King Arsaces III (Arshak III) who ruled in Western Armenia died leaving no heir. Western Armenia was annexed and became a province of the Byzantine Empire.