Answer
The Battle of Cunaxa, fought in 401 BC, marked the end of Cyrus the Younger's rebellion against his brother, King Artaxerxes II of Persia. Cyrus, supported by Greek mercenaries, attempted to seize the throne but was defeated and killed in the battle. The outcome solidified Artaxerxes' rule and put an end to the threat of a civil war within the Persian Empire.