Cyrus the Younger was defeated and killed by his brother Artaxerxes II in this battle prompted by the former's attempted usurpation of the throne.
Citation:
Bouchard, Elsa. "Battle of Cunaxa".
The Literary Encyclopedia. First published 01 March 2010
[http://www.litencyc.com/php/stopics.php?rec=true&UID=11246, accessed 20 May 2013.]