Head of king Shapur II (Sasanian dynasty A.D. 4th century). From The New York Metropolitan Museum of Art permanent collection.
The Sassanid dynasty (also Sassanian) was the name given to the kings of Persia during the era of the second Persian Empire, from 224 until 651, when the last Sassanid shah, Yazdegerd III, lost a 14-year struggle to drive out the Umayyad Caliphate, the first of the Islamic empires.
The Sassanid era began in earnest in 228, when the Shah Ardashir I destroyed the Parthian Empire which had held sway over the region for centuries. He and his successors created a vast empire, based in Firouzabad, Fars, which included those lands of the old Achaemenid Persian empire east of the Euphrates River. The Sassanids wanted to re-create the longed-for ancient empire. Zoroastrianism was made the state religion, and all other faiths were persecuted. It was the shahs' long sought-after goal to reunify all of the old Achaemenid territory, and this brought them into frequent wars against the Roman Empire and Byzantine Empire.
Shah Khosrau II (Kasrā in Arabic) fleetingly achieved this goal in a series of wars against the Byzantine Empire between 602 and 616, conquering Egypt, Syria and Palestine. However, the Byzantine Emperor Heraclius turned the tide with a daring invasion of Persia itself. In 628, Khosrau was deposed with Heraclius' army at the gates of the capital of Ctesiphon. In the peace that followed, the Sassanids retreated to their traditional frontiers.
The long war exhausted both sides, and the Sassanids were soon destroyed by the rise of Islam.
The later Sassanids were further weakened by economic decline, heavy taxation, religious unrest, rigid social stratification, the increasing power of the provincial landholders, and a rapid turnover of rulers.
Sassanid rule and the system of social stratification were reinforced by Zoroastrianism, which became the state religion.