While the Romans, after disembarking on the Asiatic shore, paused for some days to refresh themselves and to await their leader who was detained behind by religious duties, ambassadors from the great-king arrived in their camp to negotiate for peace. Antiochus offered half the expenses of the war, and the cession of his European possessions as well as of all the Greek cities in Asia Minor that had gone over to Rome; but Scipio demanded the whole costs of the war and the surrender of all Asia Minor. The former terms, he declared, might have been accepted, had the army still been before Lysimachia, or even on the European side of the Hellespont; but they did not suffice now, when the steed felt the bit and knew its rider. The attempts of the great-king to purchase peace from his antagonist after the Oriental manner by sums of money - he offered the half of his year's revenues! - failed as they deserved; the proud burgess, in return for the gratuitous restoration of his son who had fallen a captive, rewarded the great-king with the friendly advice to make peace on any terms. This was not in reality necessary: had the king possessed the resolution to prolong the war and to draw the enemy after him by retreating into the interior, a favourable issue was still by no means impossible. But Antiochus, irritated by the presumably intentional arrogance of his antagonist, and too indolent for any persevering and consistent warfare, hastened with the utmost eagerness to expose his unwieldy, but unequal, and undisciplined mass of an army to the shock of the Roman legions.
In the valley of the Hermus, near Magnesia at the foot of Mount Sipylus not far from Smyrna, the Roman troops fell in with the enemy late in the autumn of 564. The force of Antiochus numbered close on 80,000 men, of whom 12,000 were cavalry; the Romans - who had along with them about 5000 Achaeans, Pergamenes, and Macedonian volunteers - had not nearly half that number, but they were so sure of victory, that they did not even wait for the recovery of their general who had remained behind sick at Elaea; Gnaeus Domitius took the command in his stead. Antiochus, in order to be able even to place his immense mass of troops, formed two divisions. In the first were placed the mass of the light troops, the peltasts, bowmen, slingers, the mounted archers of Mysians, Dahae, and Elymaeans, the Arabs on their dromedaries, and the scythe-chariots. In the second division the heavy cavalry (the Cataphractae, a sort of cuirassiers) were stationed on the flanks; next to these, in the intermediate division, the Gallic and Cappadocian infantry; and in the very centre the phalanx armed after the Macedonian fashion, 16,000 strong, the flower of the army, which, however, had not room in the narrow space and had to be drawn up in double files 32 deep. In the space between the two divisions were placed 54 elephants, distributed between the bands of the phalanx and of the heavy cavalry. The Romans stationed but a few squadrons on the left wing, where the river gave protection; the mass of the cavalry and all the light armed were placed on the right, which was led by Eumenes; the legions stood in the centre. Eumenes began the battle by despatching his archers and slingers against the scythe-chariots with orders to shoot at the teams; in a short time not only were these thrown into disorder, but the camel-riders stationed next to them were also carried away, and even in the second division the left wing of heavy cavalry placed behind fell into confusion. Eumenes now threw himself with all the Roman cavalry, numbering 3000 horse, on the mercenary infantry, which was placed in the second division between the phalanx and the left wing of heavy cavalry, and, when these gave way, the cuirassiers who had already fallen into disorder also fled. The phalanx, which had just allowed the light troops to pass through and was preparing to advance against the Roman legions, was hampered by the attack of the cavalry in flank, and compelled to stand still and to form front on both sides - a movement which the depth of its disposition favoured. Had the heavy Asiatic cavalry been at hand, the battle might have been restored; but the left wing was shattered, and the right, led by Antiochus in person, had driven before it the little division of Roman cavalry opposed to it, and had reached the Roman camp, which was with great difficulty defended from its attack. In this way the cavalry were at the decisive moment absent from the scene of action. The Romans were careful not to assail the phalanx with their legions, but sent against it the archers and slingers, not one of whose missiles failed to take effect on the densely-crowded mass. The phalanx nevertheless retired slowly and in good order, till the elephants stationed in the interstices became frightened and broke the ranks. Then the whole army dispersed in tumultuous flight; an attempt to hold the camp failed, and only increased the number of the dead and the prisoners. The estimate of the loss of Antiochus at 50,000 men is, considering the infinite confusion, not incredible; the legions of the Romans had never been engaged, and the victory, which gave them a third continent, cost them 24 horsemen and 300 foot soldiers. Asia Minor submitted; including even Ephesus, whence the admiral had hastily to withdraw his fleet, and Sardes the residence of the court.
The king sued for peace and consented to the terms proposed by the Romans, which, as usual, were just the same as those offered before the battle and consequently included the cession of Asia Minor. Till they were ratified, the army remained in Asia Minor at the expense of the king; which came to cost him not less than 3000 talents (730,000 pounds). Antiochus himself in his careless fashion soon consoled himself for the loss of half his kingdom; it was in keeping with his character, that he declared himself grateful to the Romans for saving him the trouble of governing too large an empire. But with the day of Magnesia Asia was erased from the list of great states; and never perhaps did a great power fall so rapidly, so thoroughly, and so ignominiously as the kingdom of the Seleucidae under this Antiochus the Great. He himself was soon afterwards (567) slain by the indignant inhabitants of Elymais at the head of the Persian gulf, on occasion of pillaging the temple of Bel, with the treasures of which he had sought to replenish his empty coffers.
The Roman government, after having achieved the victory, had to arrange the affairs of Asia Minor and of Greece. If the Roman rule was here to be erected on a firm foundation, it was by no means enough that Antiochus should have renounced the supremacy in the west of Asia Minor. The circumstances of the political situation there have been set forth above[6]. The Greek free cities on the Ionian and Aeolian coast, as well as the kingdom of Pergamus of a substantially similar nature, were certainly the natural pillars of the new Roman supreme power, which here too came forward essentially as protector of the Hellenes kindred in race. But the dynasts in the interior of Asia Minor and on the north coast of the Black Sea had hardly yielded for long any serious obedience to the kings of Asia, and the treaty with Antiochus alone gave to the Romans no power over the interior. It was indispensable to draw a certain line within which the Roman influence was henceforth to exercise control. Here the element of chief importance was the relation of the Asiatic Hellenes to the Celts who had been for a century settled there. These had formally apportioned among them the regions of Asia Minor, and each one of the three cantons raised its fixed tribute from the territory laid under contribution. Doubtless the burgesses of Pergamus, under the vigorous guidance of their presidents who had thereby become hereditary princes, had rid themselves of the unworthy yoke; and the fair afterbloom of Hellenic art, which had recently emerged afresh from the soil, had grown out of these last Hellenic wars sustained by a national public spirit. But it was a vigorous counterblow, not a decisive success; again and again the Pergamenes had to defend with arms their urban peace against the raids of the wild hordes from the eastern mountains, and the great majority of the other Greek cities probably remained in their old state of dependence[7].
6. III. VIII. The Celts of Asia Minor ff.
7. From the decree of Lampsacus mentioned at III. IX. Difficulties with Rome, it appears pretty certain that the Lampsacenes requested from the Massiliots not merely intercession at Rome, but also intercession with the Tolistoagii (so the Celts, elsewhere named Tolistobogi, are designated in this document and in the Pergamene inscription, C. J. Gr. 3536, - the oldest monuments which mention them). Accordingly the Lampsacenes were probably still about the time of the wax with Philip tributary to this canton (comp. Liv. xxxviii. 16).