The Sassanids established an empire roughly within the frontiers achieved by the Achaemenids, with the capital at Ctesiphon. The Sassanids consciously sought to resuscitate Iranian traditions and to obliterate Greek cultural influence. Their rule was characterized by considerable centralization, ambitious urban planning, agricultural development, and technological improvements. Sassanid rulers adopted the title of shahanshah (king of kings), as sovereigns over numerous petty rulers, known as shahrdars. Historians believe that society was divided into four classes: the priests, warriors, secretaries, and commoners. The royal princes, petty rulers, great landlords, and priests together constituted a privileged stratum, and the social system appears to have been fairly rigid.
Sassanid rule and the system of social stratification were reinforced by Zoroastrianism, which became the state religion. The Zoroastrian priesthood became immensely powerful. The head of the priestly class, the mobadan mobad, along with the military commander, the eran spahbod, and the head of the bureaucracy, were among the great men of the state. Rome, with its capital at Constantinople, had replaced Greece as Iran's principal Western enemy, and hostilities between the two empires were frequent. Shahpur I (240-272 CE), son and successor of Ardeshir, waged successful campaigns against the Romans and in 260 CE even took the emperor Valerian prisoner. Between 260 and 263 CE he had lost his conquest to Odenathus, and ally of Rome. Shapur II (ruled 309-379 CE) regained the lost territories, however, in three successive wars with the Romans.
A rock relief at Naqsh-e Rostam, depicting the triumph of Shapur I over the Roman Emperor Valerian, and Philip the Arabian
Khosro I (531-579 CE), also known as Anushirvan the Just, is the most celebrated of the Sassanid rulers. He reformed the tax system and reorganized the army and the bureaucracy, tying the army more closely to the central government than to local lords. His reign witnessed the rise of the dihqans (literally, village lords), the petty landholding nobility who were the backbone of later Sassanid provincial administration and the tax collection system. Khosro was a great builder, embellishing his capital, founding new towns, and constructing new buildings. He rebuilt the canals and restocked the farms, which had been destroyed in the wars. He built strong fortifications at the passes and placed subject tribes in carefully chosen towns on the frontiers, so that they could act as guardians of the state against invaders. Justinian paid him 440,000 pieces of gold, as a bribe to keep the peace, but he seems to have been a man who genuinely enjoyed the fruits of peace and saw no reason to continue a senseless war. He was tolerant of all religions, though he decreed that Zoroastrianism should be the official state religion, but he was not unduly disturbed when one of his sons became a Christian. Under his auspices, too, many books were brought from India and translated into Pahlavi. Some of these later found their way into the literature of the Islamic world.
The reign of Khosro II (591-628 CE) was characterized by the wasteful splendor and lavishness of the court. Toward the end of his reign Khosro II's power declined. In renewed fighting with the Byzantines, he enjoyed initial successes, captured Damascus, and seized the Holy Cross in Jerusalem. But counterattacks by the Byzantine emperor Heraclius brought enemy forces deep into Sassanid territory.
In the spring of 633 CE a grandson of Khosro called Yezdegerd ascended the throne, and in that same year the first Arab squadrons made their first raids into Persian territory.
Years of warfare exhausted both the Byzantines and the Iranians. 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. These factors facilitated the Arab invasion in the seventh century.
It was the beginning of the end. Yezdegerd was a boy, at the mercy of his advisers, incapable of uniting a vast country which was crumbling into a number of small feudal kingdoms. Rome no longer threatened. The threat came from the small disciplined armies of Khalid ibn Walid, once one of Mohammad's chosen companion-in-arms and now, after the Prophet's death, the leader of the Arab army.
Sassanid Kings:
Ardashir I
Shapur I
Hormoz I
Bahram I
Bahram II
Bahram III
Narseh
Hormoz II
Shapur II
Ardashir II
Shapur III
Bahram IV
Yazdgerd I
Bahram V
Yazdgerd II
Hormoz III
Peroz
Balash
Kaveh I (first reign)
Zamasp
Kaveh I (second reign)
Khosro I, Anoushirvan
Hormoz IV
Bahram VI, Chobin
Khosro II, Parviz
Kaveh II
Ardashir III
Shahrvaraz
Porandokht
Hormoz V
Yazdgerd III
224 - 241 CE
241 - 272 CE
272 - 273 CE
273 - 276 CE
276 - 293 CE
293 - 293 CE
293 - 302 CE
302 - 309 CE
309 - 379 CE
379 - 383 CE
383 - 388 CE
388 - 399 CE
399 - 420 CE
420 - 438 CE
438 - 457 CE
457 - 459 CE
459 - 484 CE
484 - 488 CE
488 - 496 CE
496 - 498 CE
498 - 531 CE
531 - 579 CE
579 - 590 CE
590 - 590 CE
590 - 628 CE
628 - 628 CE
628 - 629 CE
629 - 629 CE
629 - 630 CE
630 - 632 CE
632 - 651 CE