As we all know, the Eastern Roman Empire historically fell to a mixture of barbarian invasions and a resurgent Sassanid Empire while the Western Roman Empire largely weathered the storm and even tried to retake areas of the East, lasting until Magyars who adhered to Manichaeism conquered Rome in 1472, but what if the Western Roman Empire fell and the Eastern Roman Empire survived? What PODs might be needed for such a scenario to occur? How would such a scenario affect the history of the world?