The king of Persia
In 559 BC, Cyrus succeeded his father Cambyses the Elder as King of Anshan. He apparently also soon managed to succeed Arsames to the throne of Persia though the latter was still living. Arsames was father of Hystaspes and would live to see his grandson become King Darius I of Persia. However, Cyrus was not yet an independent ruler. Like his predecessors before him, Cyrus had to recognize Median overlordship.
In his Histories, Herodotus gives a detailed description of the rise to power of Cyrus according to the best sources available to him. According to Herodotus, Cyrus was said to be part-Persian (Parsua) and part Mede and his overlord was his own grandfather Astyages who had conquered all Assyrian kingdoms apart from Babylonia. After the birth of Cyrus, Astyages had a dream that his Magi interpreted as a sign of an eventual overthrow by his grandson. He then ordered his steward Harpagus to kill the infant Cyrus. Harpagus, morally unable to kill a newborn, switched the baby with a stillborn child and reported Cyrus dead. Many years later, when Astyages discovered that his grandson was still alive, he ordered that the son of Harpagus be beheaded and served to his father on a dinner platter. Harpagus, seeking vengeance, convinced Cyrus to rally the Persian people -- then in a state of vassalage to the Medes -- to revolt ca. 554 BC–553 BC. Between 550 BC–549 BC, with the help of Harpagus, Cyrus led the Persians and his armies to capture Ecbatana, and effectively conquered Media. While he seems to have accepted the crown of Media, by 546 BC he had officially assumed the title of 'king of Persia'. Thus the Persians gained dominion over the Iranian plateau.