If the protectorate of Rome over the Hellenes was to be in Asia more than a name, an end had to be put to this tributary obligation of their new clients; and, as the Roman policy at this time declined, much more even in Asia than on the Graeco-Macedonian peninsula, the possession of the country on its own behalf and the permanent occupation therewith connected, there was no course in fact left but to carry the arms of Rome up to the limit which was to be staked off for the domain of Rome's power, and effectively to inaugurate the new supremacy among the inhabitants of Asia Minor generally, and above all in the Celtic cantons.
This was done by the new Roman commander-in-chief, Gnaeus Manlius Volso, who relieved Lucius Scipio in Asia Minor. He was subjected to severe reproach on this score; the men in the senate who were averse to the new turn of policy failed to see either the aim, or the pretext, for such a war. There is no warrant for the former objection, as directed against this movement in particular; it was on the contrary, after the Roman state had once interfered in Hellenic affairs as it had done, a necessary consequence of this policy. Whether it was the right course for Rome to undertake the protectorate over the Hellenes collectively, may certainly be called in question; but regarded from the point of view which Flamininus and the majority led by him had now taken up, the overthrow of the Galatians was in fact a duty of prudence as well as of honour. Better founded was the objection that there was not at the time a proper ground of war against them; for they had not been, strictly speaking, in alliance with Antiochus, but had only according to their wont allowed him to levy hired troops in their country. But on the other side there fell the decisive consideration, that the sending of a Roman military force to Asia could only be demanded of the Roman burgesses under circumstances altogether extraordinary, and, if once such an expedition was necessary, everything told in favour of carrying it out at once and with the victorious army that was now stationed in Asia. So, doubtless under the influence of Flamininus and of those who shared his views in the senate, the campaign into the interior of Asia Minor was undertaken in the spring of 565. The consul started from Ephesus, levied contributions from the towns and princes on the upper Maeander and in Pamphylia without measure, and then turned northwards against the Celts. Their western canton, the Tolistoagii, had retired with their belongings to Mount Olympus, and the middle canton, the Tectosages, to Mount Magaba, in the hope that they would be able there to defend themselves till the winter should compel the strangers to withdraw. But the missiles of the Roman slingers and archers - which so often turned the scale against the Celts unacquainted with such weapons, almost as in more recent times firearms have turned the scale against savage tribes - forced the heights, and the Celts succumbed in a battle, such as had often its parallels before and after on the Po and on the Seine, but here appears as singular as the whole phenomenon of this northern race emerging amidst the Greek and Phrygian nations. The number of the slain was at both places enormous, and still greater that of the captives. The survivors escaped over the Halys to the third Celtic canton of the Trocmi, which the consul did not attack. That river was the limit at which the leaders of Roman policy at that time had resolved to halt. Phrygia, Bithynia, and Paphlagonia were to become dependent on Rome; the regions lying farther to the east were left to themselves.
The affairs of Asia Minor were regulated partly by the peace with Antiochus (565), partly by the ordinances of a Roman commission presided over by the consul Volso. Antiochus had to furnish hostages, one of whom was his younger son of the same name, and to pay a war-contribution - proportional in amount to the treasures of Asia - of 15,000 Euboic talents (3,600,000 pounds), a fifth of which was to be paid at once, and the remainder in twelve yearly instalments. He was called, moreover, to cede all the lands which he possessed in Europe and, in Asia Minor, all his possessions and claims of right to the north of the range of the Taurus and to the west of the mouth of the Cestrus between Aspendus and Perga in Pamphylia, so that he retained nothing in Asia Minor but eastern Pamphylia and Cilicia. His protectorate over its kingdoms and principalities of course ceased. Asia, or, as the kingdom of the Seleucids was thenceforth usually and more appropriately named, Syria, lost the right of waging aggressive wars against the western states, and in the event of a defensive war, of acquiring territory from them on the conclusion of peace; lost, moreover, the right of navigating the sea to the west of the mouth of the Calycadnus in Cilicia with vessels of war, except for the conveyance of envoys, hostages, or tribute; was further prevented from keeping more than ten decked vessels in all, except in the case of a defensive war, from taming war-elephants, and lastly from the levying of mercenaries in the western states, or receiving political refugees and deserters from them at court. The war vessels which he possessed beyond the prescribed number, the elephants, and the political refugees who had sought shelter with him, he delivered up. By way of compensation the great-king received the title of a friend of the Roman commonwealth. The state of Syria was thus by land and sea completely and for ever dislodged from the west; it is a significant indication of the feeble and loose organization of the kingdom of the Seleucidae, that it alone, of all the great states conquered by Rome never after the first conquest desired a second appeal to the decision of arms.
The two Armenias, hitherto at least nominally Asiatic satrapies, became transformed, if not exactly in pursuance with the Roman treaty of peace, yet under its influence into independent kingdoms; and their holders, Artaxias and Zariadris, became founders of new dynasties.
Ariarathes, king of Cappadocia, whose land lay beyond the boundary laid down by the Romans for their protectorate, escaped with a money-fine of 600 talents (146,000 pounds); which was afterwards, on the intercession of his son-in-law Eumenes, abated to half that sum.
Prusias, king of Bithynia, retained his territory as it stood, and so did the Celts; but they were obliged to promise that they would no longer send armed bands beyond their bounds, and the disgraceful payments of tribute by the cities of Asia Minor came to an end. The Asiatic Greeks did not fail to repay the benefit - which was certainly felt as a general and permanent one - with golden chaplets and transcendental panegyrics.
In the western portion of Asia Minor the regulation of the territorial arrangements was not without difficulty, especially as the dynastic policy of Eumenes there came into collision with that of the Greek Hansa. At last an understanding was arrived at to the following effect. All the Greek cities, which were free and had joined the Romans on the day of the battle of Magnesia, had their liberties confirmed, and all of them, excepting those previously tributary to Eumenes, were relieved from the payment of tribute to the different dynasts for the future. In this way the towns of Dardanus and Ilium, whose ancient affinity with the Romans was traced to the times of Aeneas, became free, along with Cyme, Smyrna, Clazomenae, Erythrae, Chios, Colophon, Miletus, and other names of old renown. Phocaea also, which in spite of its capitulation had been plundered by the soldiers of the Roman fleet - although it did not fall under the category designated in the treaty - received back by way of compensation its territory and its freedom. Most of the cities of the Graeco-Asiatic Hansa acquired additions of territory and other advantages. Rhodes of course received most consideration; it obtained Lycia exclusive of Telmissus, and the greater part of Caria south of the Maeander; besides, Antiochus guaranteed the property and the claims of the Rhodians within his kingdom, as well as the exemption from customs-dues which they had hitherto enjoyed.