The march of Cyrus was directed through Lydia and Phrygia. after passing Colossae he arrived at Colaenae, where he was joined by more Greek troops, the number of whom now amounted to 11,000 hoplites and 2000 peltasts. The line of march, which had been hitherto straight upon Pisidia, was now directed northwards. Cyrus passed in succession the Phrygian towns of Peltae, Ceramon Agora, the Plain of Cayster, Thymbrium, Tyriaeum, and Iconium, the last city in Phrygia. Thence he proceeded through Lycaonia to Dana, and across Mount Taurus into Cilicia.

On arriving at Tarsus, a city on the coast of Cilicia, the Greeks plainly saw that they had been deceived, and that the expedition was designed against the Persian king. Seized with alarm at the prospect of so long a march, they sent a deputation to Cyrus to ask him what his real intentions were. Cyrus replied that his design was to march against his enemy, Abrocomas, satrap of Syria, who was encamped on the banks of the Euphrates. The Greeks, though they still suspected a delusion, contented themselves with this answer in the face of their present difficulties, especially as Cyrus promised to raise their pay from one Daric to one Daric and a half a month. The whole army then marched forwards to Issus, the last town in Cilicia, seated on the gulf of the same name. Here they met the fleet, which brought them a reinforcement of 1100 Greek soldiers, thus raising the Grecian force to about 14,000 men.

Abrocomas, who commanded for the Great King in Syria and Phoenicia, alarmed at the rapid progress of Cyrus, fled before him with all his army, reported as 300,000 strong; abandoning the impregnable pass situated one day's march from Issus, and known as the Gates of Cilicia and Syria. Marching in safety through this pass, the army next reached Myriandrus, a seaport of Phoenicia. From this place Cyrus struck off into the interior, over Mount Amanus. Twelve days' march brought him to Thapsacus on the Euphrates, where for the first time he formally notified to the army that he was marching to Babylon against his brother Artaxerxes, The water happened to be very low, scarcely reaching to the breast; and Abrocomas made no attempt to dispute the passage. The army now entered upon the desert, where the Greeks were struck with the novel sights which met their view, and at once amused and exhausted themselves in the chase of the wild ass and the antelope, or in the vain pursuit of the scudding ostrich. After several days of toilsome march the army at length reached Pylae, the entrance into the cultivated plains of Babylonia, where they halted a few days to refresh themselves.

Soon after leaving that place symptoms became perceptible of a vast hostile force moving in their front. The exaggerated reports of deserters stated it at 1,200,000 men; its real strength was about 900,000. In a characteristic address Cyrus exhorted the Greeks to take no heed of the multitude of their enemies; they would find in them, he affirmed nothing but numbers and noise, and, if they could bring themselves to despise these, they would soon find of what worthless stuff the natives were composed. The army then marched cautiously forwards, in order of battle, along the left bank of the Euphrates. They soon came upon a huge trench, 30 feet broad and 18 deep, which Artaxerxes had caused to be dug across the plain for a length of about 42 English miles, reaching from the Euphrates to the wall of Media. Between it and the river was left only a narrow passage about 20 feet broad; yet Cyrus and his army found with surprise that this pass was left entirely undefended. This circumstance inspired them with a contempt of the enemy, and induced them to proceed in careless array; but on the next day but one after passing the trench, on arriving at a place called Cunaxa, they were surprised with the intelligence that Artaxerxes was approaching with all his forces. Cyrus immediately drew up his army in order of battle. The Greeks were posted on the right, whilst Cyrus himself, surrounded by a picked body-guard of 600 Persian cuirassiers, took up his station in the centre. When the enemy were about half a mile distant, the Greeks engaged them with the usual war-shout. The Persians did not await their onset, but turned and fled. Tissaphernes and his cavalry alone offered any resistance; the remainder of the Persian left was routed without a blow. As Cyrus was contemplating the easy victory of the Greeks, his followers surrounded him, and already saluted him with the title of king. But the centre and right of Artaxerxes still remained unbroken; and that monarch, unaware of the defeat of his left wing, ordered the right to wheel and encompass the army of Cyrus. No sooner did Cyrus perceive this movement than with his body-guard he impetuously charged the enemy's centre, where Artaxerxes himself stood, surrounded with 6000 horse. The latter were routed and dispersed, and were followed so eagerly by the guards of Cyrus, that he was left almost alone with the select few called his "Table Companions." In this situation he caught sight of his brother Artaxerxes, whose person was revealed by the flight of his troops, when, maddened at once by rage and ambition, he shouted out, "I see the man!" and rushed at him with his handful of companions. Hurling his javelin at his brother, he wounded him in the breast, but was himself speedily overborne by superior numbers and slain on the spot.

Meanwhile Clearchus had pursued the flying enemy upwards of three miles; but hearing that the king's troops were victorious on the left and centre, he retraced his steps, again routing the Persians who endeavoured to intercept him. When the Greeks regained their camp they found that it had been completely plundered, and were consequently obliged to go supperless to rest. It was not till the following day that they learned the death of Cyrus; tidings which converted their triumph into sorrow and dismay. They were desirous that Ariaeus who now commanded the army of Cyrus, should lay claim to the Persian crown, and offered to support his pretensions; but Ariaeus answered that the Persian grandees would not tolerate such a claim; that he intended immediately to retreat; and that, if the Greeks wished to accompany him, they must join him during the following night. This was accordingly done; when oaths of reciprocal fidelity were interchanged between the Grecian generals and Ariaeus, and sanctified by a solemn sacrifice.

On the following day a message arrived from the Persian King, with a proposal to treat for peace on equal terms. Clearchus affected to treat the offer with great indifference, and made it an opportunity for procuring provisions. "Tell your king," said he to the envoys, "that we must first fight; for we have had no breakfast, nor will any man presume to talk to the Greeks about a truce without first providing for them a breakfast." This was agreed to, and guides were sent to conduct the Greeks to some villages where they might obtain food. Here they received a visit from Tissaphernes, who pretended much friendship towards them, and said that ha had come from the Great King to inquire the reason of their expedition. Clearchus replied--what was indeed true of the greater part of the army--that they had not come hither with any design to attack the king, but had been enticed forwards by Cyrus under false pretences; that their only desire at present was to return home; but that, if any obstacle was offered, they were prepared to repel hostilities. In a day or two Tissaphernes returned and with some parade stated that he had with great difficulty obtained permission to SAVE the Greek army; that he was ready to conduct them in person into Greece; and to supply them with provisions, for which, however, they were to pay. An agreement was accordingly entered into to this effect; and after many days delay they commenced the homeward march. After marching three days they passed through the wall of Media, which was 100 feet high and 20 feet broad. Two days more brought them to the Tigris, which they crossed on the following morning by a bridge of boats. They then marched northward, arriving in four days at the river Physcus and a large city called Opis. Six days' further march through a deserted part of Media brought them to some villages belonging to queen Parysatis, which, out of enmity to her as the patron of Cyrus, Tissaphernes abandoned to be plundered by the Greeks. From thence they proceeded in five days to the river Zabatus, or Greater Zab, having previously crossed the Lesser Zab, which Xenophon neglects to mention. In the first of these five days they saw on the opposite side of the Tigris a large city called Caenae, the inhabitants of which brought over provisions to them. At the Greater Zab they halted three days. Mistrust, and even slight hostilities, had been already manifested between the Greeks and Persians, but they now became so serious that Clearchus demanded an interview with Tissaphernes. The latter protested the greatest fidelity and friendship towards the Greeks, and promised to deliver to the Greek generals, on the following day, the calumniators who had set the two armies at variance. But when Clearchus, with four other generals, accompanied by some lochages or captains, and 200 soldiers, entered the Persian camp, according to appointment; the captains and soldiers were immediately cut down; whilst the five generals were seized, put into irons, and sent to the Persian court. After a short imprisonment, four of them were beheaded; the fifth, Menon, who pretended that he had betrayed his colleagues into the hands of Tissaphernes, was at first spared; but after a year's detention was put to death with tortures.

Apprehension and dismay reigned among the Greeks. Their situation was, indeed, appalling. They were considerably more than a thousand miles from home, in a hostile and unknown country, hemmed in on all sides by impassable rivers and mountains, without generals, without guides, without provisions. Xenophon was the first to rouse the captains to the necessity for taking immediate precautions. Though young, he possessed as an Athenian citizen some claim to distinction; and his animated address showed him fitted for command. He was saluted general on the spot; and in a subsequent assembly was, with four others, formally elected to that office.

The Greeks, having first destroyed their superfluous baggage, crossed the Greater Zab, and pursued their march on the other bank. They passed by the ruined cities of Larissa and Mespila on the Tigris, in the neighbourhood of the ancient Nineveh. The march from Mespila to the mountainous country of the Carduchi occupied several days in which the Greeks suffered much from the attacks of the enemy.