Our knowledge of his personal history begins with what he himself recounts in the Anabasis. His friend Proxenus, then at Sardis commanding a regiment of Hellenic mercenaries under Cyrus the younger, wrote recommending him earnestly to come over and take service, in the army prepared ostensibly against the Pisidians. Upon this Xenophon asked the advice of Sokrates: who exhorted him to go and consult the Delphian oracle--being apprehensive that as Cyrus had proved himself the strenuous ally of Sparta, and had furnished to her the principal means for crushing Athens, an Athenian taking service under him would incur unpopularity at home. Xenophon accordingly went to Delphi: but instead of asking the question broadly--"Shall I go, or shall I decline to go?"--he put to Apollo the narrower question--"Having in contemplation a journey, to which of the Gods must I sacrifice and pray, in order to accomplish it best, and to come back with safety and success?" Apollo indicated to him the Gods to whom he ought to address himself: but Sokrates was displeased with him for not having first asked, whether he ought to go at all. Nevertheless (continued Sokrates), since you have chosen to put the question in your own way you must act as the God has prescribed.[6] [Footnote 6: Xenoph. Anab. iii. 1, 4-6.] [Side-note: His service and command with the Ten Thousand Greeks; afterwards under Agesilaus and the Spartans.--He is banished from Athens.] The anecdote here recounted by Xenophon is interesting, as it illustrates his sincere faith, as well as that of Sokrates, in the Delphian oracle: though we might have expected that on this occasion, Sokrates would have been favoured with some manifestation of that divine sign, which he represents to have warned him afterwards so frequently and on such trifling matters. Apollo however was perhaps displeased (as Sokrates was) with Xenophon, for not having submitted the question to him with full frankness: since the answer given was proved by subsequent experience to be incomplete.[7] After fifteen months passed, first, in the hard upward march--next, in the still harder retreat--of the Ten Thousand, to the preservation of whom he largely contributed by his energy, presence of mind, resolute initiative, and ready Athenian eloquence, as one of their leaders--Xenophon returned to Athens. It appears that he must have come back not long after the death of Sokrates. But Athens was not at that time a pleasant residence for him. The Sokratic companions shared in the unpopularity of their deceased master, and many of them were absent: moreover Xenophon himself was unpopular as the active partisan of Cyrus. After a certain stay, we know not how long, at Athens, Xenophon appears to have gone back to Asia; and to have resumed his command of the remaining Cyreian soldiers, then serving under the Lacedæmonian generals against the Persian satraps Tissaphernes and Pharnabazus. He served first under Derkyllidas, next under Agesilaus.