Silver plate showing Shapur II

In about AD 224 the Parthians were defeated by Ardashir, a descendant of Sasan who gave his name to the new Sasanian dynasty. They were to rule Iran for over 400 years and saw themselves as the successors to the Achaemenid Persians. One of the most energetic and able Sasanian rulers was Shapur I (AD 240-72). In his reign the central government was strengthened, the coinage was reformed and Zoroastrianism was made the state religion. The expansion of Sasanian power brought them into conflict with Rome in the west. In AD 260 the emperor Valerian was taken prisoner by Shapur I in a battle near Edessa. After this the defence of Rome's eastern frontier was left to the ruler of Palmyra, a caravan city in Syria that was allied with Rome, and his wife Zenobia. By the end of the reign of Shapur I, the Sasanian empire stretched from the River Euphrates to the River Indus and included modern-day Armenia and Georgia. After a short period during which much territory was lost. Sasanian fortunes were restored during the long reign of Shapur II.