A Border without a Line? Mental Frontiers between Roman Armenia and Persarmenia after 387

For many historians, the division of Armenia in 387 into Roman and Sasanian Iranian territories is a well-defined historical marker. The reality is much more complex than this, as contemporary sources reveal a “border” that was a primarily a diplomatic creation rather than a genuine physical divide. This study argues that the cartographic clarity often imposed by modern scholarship is an anachronistic projection, reflecting contemporary preferences for order onto a Late Antique landscape that was inherently ambiguous. This ambiguity was embedded in Armenian society itself. The dominance of the naxarar, semi-autonomous noble houses with shifting allegiances, rendered the enforcement of a fixed frontier nearly impossible. By contrasting the structured administrative systems of Rome with the kinship-based territoriality of Armenian lords, this paper contends that the 387 division constituted a conceptual framework for imperial management rather than a tangible boundary. Ultimately, the border emerged as a fluid outcome of a deeply fragmented society.