The Classical Armenian periphrastic perfect consists of a participle in -eal and an initially optional form of a copulative verb. Over the course of the fifth century CE, one copula, em ‘to be’, grammaticalises into a standard, unmarked major use pattern in a process of obligatorification; patterns with other copulas such as linim ‘to become’ and kam ‘to stand, remain’ are retained to a lesser extent and with more specific aspectual semantics. This paper outlines the development of these constructions over the course of the fifth and early sixth centuries on the basis of a corpus of historiographical texts and draws out parallels with the neighbouring West Middle Iranian languages.