The Parthians were a nomad people from the great steppe region beyond the Caspian Sea. They came to power after Antiochus III, King of Seleucia, was defeated by the Romans in Lydia in 190 BC.
The Parthian king Mithridates I began a period of conquest which resulted in the Parthian military aristocracy ruling a vast Iranian empire. The settled Persians in southern Iran, however, were never content at being dominated by their northern nomadic neighbours.
The Parthian imperial government worked on a feudal basis. Society was dominated by seven great clans who supported a petty aristocracy. The king was a member of one of the clans, and loyalty was strong between the great clan leaders and their vassals.
At the bottom of society were the native Iranians, who were generally peasants and serfs.
The Parthian crown was not inherited: kings were elected on merit by the aristocratic clan leaders. This system often led to rivalry and instability, and was a major factor in their losing control of the empire to the Sassanians in AD 226.
