Titus Livius (Livy), The History of Rome, Book 37
Evan T. Sage, PhD professor of latin and head of the department of classics in the University of Pittsburgh, Ed.

18. About the same time Seleucus, the son of Antiochus, [2??] after holding the army in Aeolis for the whole period of the winter, partly assisting his allies, partly plundering those whom he could not win over to his alliance, decided to invade the territory of Eumenes while he was far from home, engaged with the Romans and Rhodians in the naval operations off Lycia. [3] He first approached Elaea with his army formed for battle; then, abandoning the attack on the city, he devastated the fields in hostile fashion, [p. 343]and marched off to lay siege to Pergamum, the chief¹ city and citadel of the kingdom. [4] Attalus² at first, stationing outposts before the city and organizing raids of the cavalry and light infantry, harassed rather than resisted the enemy; [5] finally, when, after learning from such skirmishing that he was equal in no aspect of his strength, he had retired within the walls, the siege of the city began. [6] About the same time Antiochus also set out from Apamea and established a base first at Sardis, then at the mouth of the Caicus river, with a great army composed of men of various nationalities. The greatest source of terror consisted of four thousand Gauls who served for pay. [7] These troops, with a few others intermixed,³ he sent to lay waste the territory of Pergamum in every direction. [8] When the news of this reached Samos, Eumenes, called away by the war at home, first went to Elaea with his fleet; then, since cavalry and light infantry were at hand, protected by their guard, before the enemy discovered it or made any move, he hastened to Pergamum. Then again small battles began to take place, growing out of raids, Eumenes without doubt avoiding a decisive engagement. [9] A few days later the Roman and Rhodian fleets came to Elaea from Samos to assist the king. [10] When it was reported to Antiochus that they had landed their troops at Elaea and that so many fleets had assembled in one harbour, and when about the same time he had learned that the consul with his army was already in Macedonia and [p. 345]was making ready what was necessary for the passage⁴ of the Hellespont, he decided that the time had come, before he should be beset on land and sea at once, to treat for peace, and he occupied with his camp a hill facing Elaea; [11] there, leaving all his infantry forces in camp, with the cavalry, numbering six thousand, he [12??] went down into the open country under the very walls of Elaea and sent a herald to Aemilius to say that he wished to discuss the question of peace.⁵