In AD 224 Ardashir I, a Persian Vassal-King, rebelled against the Parthians, defeated them in the Battle of Hormuz, and founded a new Persian dynasty, that of the Sassanids. He then conquered several minor neighboring kingdoms, invaded Iindia, levying heavy tribute from the rulers of the Punjab, and conquered Armenia. Ardashir was succeeded in 241 by his son Shapur I, who waged two successive wars against the Roman Empire. Between 260 and 263 he lost his conquests to Odenathus, Prince of Palmyra, and ally of Rome.
The Sassanids were last dynasty of native rulers to reign in Persia before the Arab Conquest. The period of their dominion extended from 224 AD, when the Parthians were overthrown until 640 AD, when the country fell under the power of the arabs. The name of the Dynasty was derived from Sassan, an ancestor of the founder of the dynasty, Ardashir I. Shapur I was king of Persia from 241 until 272 AD. He was the son and successor of Ardashir I, of the Sassanian Dynasty.
He was an able warrior king, although he was defeated by the Roman Emperor, Gordian III, in 242. Gordian’s successor, Philip the arabian, concluded a peace with Shapur guaranteeing his power in Armenia and Mesopotamia. In 260 he achieved his greatest triumph by defeating the Roman Emperor Valerian. Despite the need for constant vigilance and response to the Roman threat, Shapur not only maintained Persian power in the west but also rebuilt the Persian economy. He promoted a program of public works, and in later years he commissioned the translation of numerous Greek and Indian writings.
War with Rome was renewed by Narses; his army was almost annihilated by Roman forces in 297, and he was compelled to conclude peace terms whereby the western boundary of Persia was moved from the Euphrates River to the Tigris River and much additional territory was lost.
Shapur II (ruled 309-379) regained the lost territories, however, in three successive wars with the Romans.