Xenophon (435-354 B.C.) was historian, philosopher, and military commander, born at Athens, son of an Athenian of good position; was a pupil and friend of Socrates; joined the expedition of Cyrus against his brother Artaxerxes, and on the failure of it conducted the ten thousand Greeks—“the Retreat of the Ten Thousand”—who went up with him back to the Bosphorus, served afterwards in several military adventures, brought himself under the ban of his fellow-citizens in Athens, and retired to Elis, where he spent 20 years of his life in the pursuits of country life and in the prosecution of literature; the principal of his literary works, which it appears have all come down to us, are the “Anabasis,” being an account in seven books of the expedition of Cyrus and his own conduct of the retreat; the “Memorabilia,” in four books, being an account of the life and teaching and in defense of his master Socrates; the “Helenica,” in seven books, being an account of 49 years of Grecian history in continuation of Thucydides to the battle of Mantinea; and “Cyropædeia,” in eight books, being an ideal account of the education of Cyrus the Elder. Xenophon wrote pure Greek in a plain, perspicuous, and unaffected style, had an eye to the practical in his estimate of things, and professed a sincere belief in a divine government of the world .
Xenophon was the primary historian of the last days of Greece's freedom. His Memorabilia depicts Socrates as a teacher of virtue who balanced reason and faith in order to attain the truth.  He wrote a detailed account Hellenica which picked up where Thucydides's History of the Peloponnesian War left off.
Xenophon's most famous work is the "Anabasis" or "Upland March", which describes the march of the 10,000 Greek mercenaries through Anatolia to get back to Greece. It is read as a basic text in ancient Greek.