In May 401 the Persian prince, Cyrus the Younger, set out from his satrapy in western Anatolia to pacify a tribe of the interior. His army comprised levies drawn from the areas under his command and some 12,000 Greek mercenaries. However, unknown to all but a few of these men, his real destination was Babylonia, his true aim, to seize the royal throne from his older brother. Although he managed to lead the force into the heart of Mesopotamia, Cyrus was killed in the ensuing battle with King Artaxerxes, who went on to reign for forty years more. With Cyrus dead, the Persians had no serious incentive to destroy his Greek mercenaries and instead led them northward out of Mesopotamia. After seizing their generals in a ruse at the Zapatas River, they funnelled the men into the highlands of the Kardouchoi, a fiercely independent people once said to have destroyed a large contingent sent by the King to pacify them. The satrap Tissaphernes, who had orchestrated the removal of the Greeks from Babylonia, must have been confident as he rode west to take over Cyrus's dominion that he would not see or hear of them again as a unit. Yet they managed to fight through the territory of the Kardouchoi and, eventually, to make their way to the Black Sea. Within two years, those who had survived the retreat were on the offensive against Tissaphernes as part of a Spartan-led force in Asia Minor.

One of the Greeks on the march, Xenophon of Athens, later wrote an account of Cyrus's expedition and its aftermath. Offering an eyewitness version of events, it succeeds in conveying a palpable sense of the trials endured by the army as it fought its way home from the heart of Persian territory. Yet the work is at once more than and not quite a personal history of the expedition and retreat. Xenophon, who becomes the key protagonist in the story, refers to himself in the third person, and this ‘Xenophon’ appears more like an exemplar than a historical figure. Moreover, the intense focus on Xenophon's character throughout Books 3–7 is at the expense of a more balanced view of events.