[448] Arrian, iii. 24, 4. In reference to the mountain tribes called Mardi, who are mentioned in several different localities—on the parts of Mount Taurus south of the Caspian, in Armenia, on Mount Zagros, and in Persis proper (see Strabo, xi. p. 508-523; Herodot. i. 125), we may note, that the Nomadic tribes, who constitute a considerable fraction of the population of the modern Persian Empire, are at this day found under the same name in spots widely distant: see Jaubert, Voyage en Arménie et en Perse, p. 254. From this march, which had carried him in a westerly direction, he returned to Hyrkania. At the first halt he was met by the Grecian mercenaries who came to surrender themselves, as well as by various Grecian envoys from Sparta, Chalkedon, and Sinôpe, who had accompanied Darius in his flight. Alexander put the Lacedæmonians under arrest, but liberated the other envoys, considering Chalkedon and Sinôpe to have been subjects of Darius, not members of the Hellenic synod. As to the mercenaries, he made a distinction between those who had enlisted in the Persian service before the recognition of Philip as leader of Greece—and those whose enlistment had been of later date. The former he liberated at once; the latter he required to remain in his service under the command of Andronikus, on the same pay as they had hitherto received.[449] Such was the untoward conclusion of Grecian mercenary service with Persia; a system whereby the Persian monarchs, had they known how to employ it with tolerable ability, might well have maintained their empire even against such an enemy as Alexander.[450] [449] Arrian, iii. 24, 8; Curtius, vi. 5, 9. An Athenian officer named Demokrates slew himself in despair, disdaining to surrender. [450] See a curious passage on this subject, at the end of the Cyropædia of Xenophon.