In 401, being invited by his friend Proxenus to join the expedition of the younger Cyrus against his brother, Artaxerxes II. of Persia, he at once accepted the offer. It held out the prospect of riches and honor, while he was little likely to find favor in democratic Athens, where the knights were regarded with suspicion as having supported the Thirty. At the suggestion of Socrates, Xenophon went to Delphi to consult the oracle; but his mind was already made up, and he at once proceeded to Sardis, the place of rendezvous. Of the expedition itself he has given a full and detailed account in his Anabasis, or the "Up-Country March." After the battle of Cunaxa (401), in which Cyrus lost his life, the officers in command of the Greeks were treacherously murdered by the Persian satrap, Tissaphernes, with whom they were negotiating an armistice with a view to a safe return. The army was now in the heart of an unknown country, more than a thousand miles from home and in the presence of a troublesome enemy. It was decided to march northwards up the Tigris valley and make for the shores of the Euxine, on which there were several Greek colonies. Xenophon became the leading spirit of the army; he was elected an officer, and he it was who mainly directed the retreat. Part of the way lay through the wilds of Kurdistan, where they had to encounter the harassing guerrilla attacks of savage mountain tribes, and part through the highlands of Armenia and Georgia. After a five months' march they reached Trapezus [Trebizond on the Euxine (February 400), where a tendency to demoralization began to show itself, and even Xenophon almost lost his control over the soldiery. At Cotyora he aspired to found a new colony; but the idea, not being unanimously accepted, was abandoned, and ultimately Xenophon with his Greeks arrived at Chrysopolis [Scutari] on the Bosporus, opposite Byzantium.