What role did Cyrus the Great play in Persian history?

Persia was a vassal state of Media. He absorbed Media into Persia, and together he led them to defeat the Babylonian Empire, absorb it, and went on to take over all of the Middle East, and Central Asia. This left his successors to consolidate this empire by adding Egypt, Thrace and western India, and develop stable government of the empire which lasted for 200 years until it was taken over by Alexander the great's Macedonia..