 Ardashir extended the Persian Empire to Oxus in the north-east, to the Euphrates in the west, and on his death bed in 241, he passed on his crown to Shapur, who would carry on the war further into Rome.The Sassanid Dynasty revived the old Achaemenid traditions, including Zoroastrianism, as Ardashir had promised.However, exhausting wars with Byzantium left the empire unready to face the Muslim armies from Arabia.