Explanation: In the last Byzantine-Sassanid War, the Byzantines (or the Eastern Roman Empire, depending on your taste for nomenclature) and the Persian Sassanids spent the better part of ~30 years butchering each other for no real gain. At the end of it all, the two sides decided to make what was essentially a white peace - no gains, no losses (other than the butchery that had exhausted both states).

… a few years later, the Rashidun Caliphate carrying the banner of the new faith of Islam emerged out of the Arabian peninsula, and overran both war-worn states - Persia entirely, and the Byzantines from Egypt to Africa.