An empire that occupied much of south-west Asia from the 3rd to the 7th century. It was founded c.224 by Ardashir (ruled c.224–41), who overthrew Artabanus V, the last Parthian king, in the name of vengeance for the last Achaemenid king. The dynasty takes its name from his grandfather Sasan. Territorially the empire stretched from the Syrian desert, where Roman pressure was checked, to north-west India where the Kushan and Hephthalite empires, having restricted valuable trade routes, were eventually destroyed. Politically the empire fluctuated between centralization under strong monarchs like Khosrau I (died 579), who were served by the army and bureaucracy, and local control by great nobles. The religious life of the empire was dominated by Zoroastrianism, established as the state cult in the 3rd century. Christians in Armenia and Transcaucasia survived persecution and, by breaking with the Byzantine Church in 424, threw off the suspicion of alien loyalties. The court at Ctesiphon (in modern Iraq) provided a focus for a brilliant culture, enriched by Graeco-Roman and eastern influences, in which such pastimes as chess and polo were played. The closing years of the dynasty were overshadowed for the masses, however, by lengthy wars, which may explain the empire’s rapid disintegration before the Arab conquest of 636–51.