This is nonsense, of course, especially regarding the Sasanian state. The same peoples, cultures, and religions were found on either side of the frontier, and the Sasanian government was eager to appropriate the customs and patrimony of Rome. The reverse is also true, but I will leave that for later. The Persian kings held church synods, spread rumours that they had converted, and sent Christian missionaries to the nomads of Inner Asia. Mutual adoptions were proposed between ruling families and cabals. Kings and emperors were deposed and installed with Roman or Persian help. Sasanian kings frequented and patronised saints' shrines, took Roman wives, and installed bishops. At least one Roman pretender was crowned in Ctesiphon. And, finally, despite periods of mutual hostility, Iran and Rome together managed to regulate mutual trade, warfare, exchange of prisoners, construction of fortresses, protection of religious minorities, inter alia, through a series of treaties approximating what we would now call international law. And there is also the famous story of Khusro I welcoming the professors of the shuttered Athenian Neoplatonic academy at Ctesiphon. QED!