It was at the close of the Peloponnesian War that Darius II., King of Persia, died, leaving two sons, Artaxerxes and Cyrus. These two heirs could not agree which should reign. Artaxerxes claimed the throne because he was the elder, and Cyrus because he was the first son born after their father had become king; for in Persia it was the custom for a ruler to choose as his successor a son born after he had taken possession of the throne.

The quarrel between the two brothers daily became more bitter; and when Artaxerxes made himself king by force, Cyrus swore that he would compel him to give up his place again.