Xenophon was an Athenian knight, an associate of Socrates, who is known for his chronicles of a mercenary expedition against Persia and the subsequent history of Greece. The expedition, called the Anabasis, was led by Cyrus against his older brother, the Persian emperor Artaxerxes II. A battle took place at Cunaxa, where the Greeks were victorious but Cyrus was killed, and shortly thereafter the general Clearchus of Sparta was apprehended and executed. The mercenaries found themselves deep in hostile territory, far from the sea, and without leadership. But they elected new leaders, including Xenophon himself, who led them north through Armenia and back to Greece.
Afterwards, Xenophon retired to Athens, but finding the city to be unfriendly, rejoined his comrades and helped the Spartans against Persia. When Athens allied with Persia against Sparta, he was banished, and spent the next few decades at Scillus, where his Anabasis was put together. Later the banishment was revoked, and Xenophon spent his last years at Athens.