Cyrus the Great had already succeeded to the Persian throne in 559 BCE though his father lived for another eight years; however, Cyrus was not yet an independent ruler.

Like his predecessors, Cyrus had to recognize Median overlordship.

The Median Empire during Astyages's reign, may have ruled over the majority of the Ancient Near East, from the Lydian frontier in the west to the Parthians and Persians in the east.

In Herodotus's version, the Median general Harpagus, seeking vengeance, persuaded Cyrus to rally the Persian people to revolt against their feudal lords, the Medes.

It is likely, however, that both Harpagus and Cyrus rebelled due to their dissatisfaction with Astyages's policies.

From the start of the revolt in summer 553 BCE, with his first battles taking place from early 552 BCE, Harpagus, with Cyrus, led his armies against the Medes until the capture of Ecbatana in 549 BCE, effectively conquering the Median Empire.

While Cyrus the Great seems to have accepted the crown of Media, by 546 BCE, he officially assumes the title "King of Persia" instead.

With Astyages out of power, all of his vassals (including many of Cyrus's relatives) are now under his command.

His uncle Arsames, who had been the king of the city-state of Parsa under the Medes, therefore would have had to give up his throne.

However, this transfer of power within the family seems to have been smooth, and it is likely that Arsames was still the nominal governor of Parsa, under Cyrus's authority—more of a Prince or a Grand Duke than a King.

His son, Hystaspes, who was also Cyrus's second cousin, was then made satrap of Parthia and Phrygia.

Cyrus the Great thus united the twin Achaemenid kingdoms of Parsa and Anshan into Persia proper.

Arsames would live to see his grandson become Darius the Great, Shahanshah of Persia, after the deaths of both of Cyrus's sons.

Cyrus makes Media a province in his new empire, forming a lasting union of the Persians and the Medes.

His conquest of Media is merely the start of his wars.