After completing his mission with the Cadusians and signing a peace treaty with Anaphernes, Cyrus returned to Media. In Ecbatana, Harpagus, who harbored a deep resentment towards Astyages, strongly encouraged Cyrus to disobey the Median king. Harpagus, who had managed to gather a group of Astyages's opponents around him, promised Cyrus that he and his allies would support him if he rebelled. He spoke of Astyages's corruption, tyranny, and oppression, and Cyrus, who had witnessed these corruptions during his stay at the Median court, assented to Harpagus's requests.
With the help of Harpagus and his allies, Cyrus managed to secretly send a messenger to his father, Cambyses, in Parsa. He asked Cambyses to prepare an army under the pretext of aiding Astyages in the war against the Cadusians and march towards Media. Meanwhile, with the help of Harpagus and his allies, he managed to escape from Ecbatana and make his way towards Anshan. He knew that at any moment, news of his escape could reach Astyages, and this would mean the beginning of a great battle.
When news of Cyrus's escape reached the Median king, he became enraged and shouted: "Pursue Cyrus immediately, bring him back to us, and if he falters in carrying out our command, sever his head from his body." Immediately, three hundred swift Median cavalrymen galloped furiously from Ecbatana in pursuit of Cyrus. It wasn't long before the cavalry caught up with Cyrus and relayed Astyages's command to him.
Cyrus feigned obedience, but used the darkness of the night as an excuse to rest, proposing to return to Astyages at dawn. He sacrificed and roasted sheep in the Persian manner, prepared a lavish dinner for them, and gave them plenty of wine until they all became drunk and unconscious. Then, secretly and in the silence of the night, he set off towards Parsa, leaving the Median cavalry in a drunken slumber.
Near the city of Hyrba, seven hundred cavalry and five thousand infantry sent by Cambyses to aid his son reached him. Cyrus immediately ordered his soldiers to form a battle array and positioned himself on the right flank. At dawn, the Median cavalry realized what had happened and pursued Cyrus with anger and anxiety. When they reached the city of Hyrba, they saw the Persian forces ready for battle.
Cyrus, who was positioned on the right flank with the cavalry, ordered the attack. He struck the heart of the Median cavalry like a fierce lion, bringing down many of them. The Persians, witnessing Cyrus in battle for the first time, were astonished by his bravery and strength. Approximately two hundred and fifty Median cavalrymen were annihilated by the Persians, and the remaining fled to save themselves. The cavalrymen who managed to survive the battle reported the incident to Astyages.
Cyrus also returned to Parsa with his troops. With this event, the war between the Medes and the Persians began. At this pivotal moment, young Cyrus, who had reviewed all these historical events with his modern mind, reached a decisive conclusion. He understood that his destiny and his grandfather's fear of him were unchangeable, and that attempts to conceal his genius were futile. From then on, he decided not only to no longer hide his abilities but also to implement more reforms and innovations, relying on his 21st-century knowledge. He intended to accelerate Astyages's downfall by increasing his influence among the people and nobles of Parsa, and even Media, and to soon seize control to build his thousand-year empire.