Since Ardashir’s victory over the Parthians in A.D 224 to his successors’ eventual collapse at the hands of the Arabs in 651 the Roman and Sasanian Empires had been bitter and deadly rivals. Throughout Late Antiquity the Roman-Sasanian relationship was dominated by competition; a constant battle for imperial prestige, military supremacy, cultural influence and economic advantage. In the course of their relationship Ctesiphon, the Sasanian capital, had been sacked by Roman forces, the Roman emperor Valerian had been captured and taken prisoner, Julian the Apostate was killed by Sassanian forces in his infamous 363 campaign and the great Roman city of Antioch had been captured and razed.

Yet in this seemingly never-ending imperial struggle the fifth century stands out as a period of unprecedented peace, and even cooperation, between the imperial rivals. It is therefore the aim of this thesis to analyse what made the fifth century uniquely a period of peace between these two ancient superpowers. By investigating all aspects of the relationship; military conflicts, barbarian threats, religious and cultural issues, economic considerations and the development of diplomatic contacts it will be possible to conclude what pushed the two empires towards a peaceful settlement and how this peace was maintained in the face of old hostilities and traditional antagonism.