Cyrus is reportedly the son of Cambyses,…

Cyrus is reportedly the son of Cambyses, a prince in Persis (modern Fars province) and whose mother (according to Herodotus) is the daughter of Median king Astyages, who in 559 ruled the Persian district of Anshan. (The name Cyrus may simply mean simply "son" in a local dialect.)

Named as Astyages’ heir (though his father will live until 551 BCE) Cyrus succeeds to the throne of Anshan in 559 BCE; however, he is not yet an independent ruler.

Like his predecessors, Cyrus has to recognize Median overlordship.

During Astyages's reign, the Median Empire 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, Harpagus, seeking vengeance, persuades Cyrus to rally the Persian people to revolt against their feudal lords, the Medes.

However, it is likely 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, leads his armies against the Medes until the capture of Ecbatana in 549 BCE, effectively conquering the Median Empire.