The nearly four centuries of Sasanian rule which separate the accession of Ardashir, which have long been viewed as a period of bitter enmity between the Iranian and Roman empires. Persian mercenaries were to be found in the imperial armies, and the presence of Mazdeans on Byzantine territory is revealed by the clauses guaranteeing their religious freedom incorporated in peace treaties. All the repeated attempts of the official Nestorian Church of Persia to dissociate itself from Byzantium and stress its disagreements with Constantinopolitan doctrine, all the protestations by Persian church councils of their loyalty to the king of kings failed to break altogether the accepted equation of Christian with Byzantine supporter and to disabuse the Sasanian authorities. The powerful impact of Greek art on Sasanian Persia and vice versa. Particularly remarkable is the seeming absence of any such revival in the early days of Khusrau II, in the period of closest political co-operation between Iran and Byzantium.