Xenophon.

The fourth century had many historians, but only a small portion of their output remains. The author with the best survival record is Xenophon, an Athenian of good family and a member of Socrates' circle. Against Socrates' advice he joined a corps of Greek mercenaries in the army which Cyrus, the younger brother of the Persian king, mustered in 401 B.C.E. to usurp the throne. The expedition was a disaster, but Xenophon led them safely out to the Black Sea coast, and from there they dispersed to seek other employers. Xenophon himself took service with the Spartans. Athens exiled him shortly after Socrates' death—he would return to Athens only in 365 B.C.E.—and he lived on a estate granted him by Sparta for much of his banishment until the upheavals after Sparta's defeat at Leuctra in 372 B.C.E. forced...