Although only his books on the Roman Civil Wars survive in their entirety, large parts of Appian's book on the Syrian War, or Syriaca, have also come down to us. This book deals with the war that the Romans and the Seleucid king Antiochus III the Great fought in 192-188, but also discusses, as an appendix, the history of the Seleucid Empire. The Syriaca is a valuable source for the history of the ancient Near East between the reign of Alexander the Great and the Roman conquest.
The translation was made by Horace White; notes by Jona Lendering.
The Romans invade Asia (cont'd)
 About this time Seleucus,note[190 BCE; this Seleucus was the future king Seleucus IV Philopator (r. 187-175).] the son of Antiochus, ravaged the territory of Eumenes and laid siege to Pergamon, shutting up the soldiers in it. On account of this Eumenes sailed with haste to Elaea, the naval station of his kingdom, and with him Lucius Aemilius Regillus, the successor of Livius as admiral.
One thousand foot-soldiers and 100 picked horse had been sent by the Achaeans as allies to Eumenes. When their commander, Diophanes, from the wall saw the soldiers of Seleucus sporting and drinking in a contemptuous way, he urged the Pergameans to join him in a sally against the enemy.
As they would not agree to this he armed his 1000 foot and his 100 horse, led them out of the city under the wall, and stood there quietly. The enemy derided him for a long time on account of the smallness of his force and because he did not dare to fight, but he fell upon them while they were taking their dinner, threw them into confusion, and put their advance guard to flight. While some sprang for their arms, and others tried to bridle their horses or to catch those that ran away or to mount those that would not stand, Diophanes won a most glorious victory, the Pergameans cheering vociferously from the walls, but even then not venturing out. Having killed as many as he could in a brief demonstration and taken a certain number of prisoners with their horses, he quickly returned.
The following day he again stationed the Achaeans under the wall, the Pergameans again not going out with him. Seleucus approached him with a large body of horse and challenged him to battle, but Diophanes did not accept the challenge. He kept his station close under the wall and watched his opportunity. Seleucus remained till midday, when he turned and led his tired horsemen back.
Then Diophanes fell upon his rear and threw it into confusion, and after doing all the damage he could, returned forthwith to his place under the wall. By continually stealing upon the enemy in this way whenever they were collecting forage or wood, and inflicting losses upon them, he compelled Seleucus to move away from Pergamon, and finally drove him out of Eumenes' territory altogether.
 Not long afterward Polyxenidas and the Romans had a naval engagement near Myonnesus, in which the former had ninety decked ships, and Regillus, the Roman admiral, eighty-three, of which twenty-five were from Rhodes. The latter were ranged by their commander, Eudorus, on the left wing.
Seeing Polyxenidas on the other wing extending his line much beyond that of the Romans, and fearing lest it should be surrounded, he sailed rapidly around there with his swift ships and experienced oarsmen, and brought his fire-ships against Polyxenidas first, scattering flames everywhere. The ships of the latter did not dare to meet their assailants on account of the fire, but, sailing round and round, tried to keep out of the way, shipped much water, and were exposed to ramming behind the bows.
Presently a Rhodian ship struck a Sidonian, and the blow being severe the anchor of the latter was dislodged and stuck in the former, fastening them together. The two ships being immovable the contest between the crews became like a land fight. As many others hastened to the aid of each, the competition on both sides became spirited, and the Roman ships broke through the Antiochean line of battle, which was exposed in this way, and surrounded the enemy before they knew it.
When they discovered it there was a flight and a pursuit. Twenty-nine of the Antiochean ships were lost, thirteen of which were captured with their crews. The Romans lost only two vessels. Polyxenidas captured the Rhodian ship and brought it to Ephesus.
The battle of Magnesia
 Such was the result of the naval engagement at Myonnesus. Before Antiochus heard of it he was fortifying the Chersonesus and Lysimacheia with the greatest care, thinking, as was the fact, that this was very important as a defense against the Romans, who would have found it very difficult to pass, or to get through the rest of Thrace, if Philip had not conducted them.
But Antiochus, who was generally fickle and light-minded, when he heard of his defeat at Myonnesus was completely panic-stricken, and thought that his evil genius had conspired against him. Everything had turned out contrary to his expectations. The Romans had beaten him on the sea, where he thought he was much superior. The Rhodians had shut Hannibal up in Pamphylia. Philip was helping the Romans over the impassable roads, whereas Antiochus supposed that he would have a lively remembrance of what he had suffered from them. Everything unnerved him, and the deity took away his reasoning powers (as is usually the case when misfortunes multiply), so that he abandoned the Chersonesus without cause, even before the enemy came in sight, neither carrying away nor burning the great stores which he had collected there of grain, arms, money, and engines, but leaving all these sinews of war in good condition for the enemy.
He paid no attention to the Lysimacheans who, as though after a siege, with lamentations accompanied him in his flight, together with their wives and children. He was intent only upon preventing the enemy from crossing at Abydus, and rested his last hope of success wholly on that. Yet he was so beside himself that he did not even defend the crossing, but hastened to reach the interior in advance of the enemy, not even leaving a guard at the straits.
 When the Scipios learned of his flight they took Lysimacheia on their march, possessed themselves of the treasure and arms in the Chersonesus, crossed the unguarded Hellespont in haste in order to arrive at Sardes before Antiochus, who did not yet know that they had crossed.
The panic-stricken king, charging his own faults to the score of fortune, sent Heraclides the Byzantine to the Scipios to treat for peace. He offered to give them Smyrna, Alexandria on the Granicus, and Lampsacus, on account of which cities the war had been begun, and to pay them half the cost of the war. He was authorized if necessary to surrender the Ionian and Aeolian cities which had sided with the Romans in the fight and whatever else the Scipios might ask. These things Heraclides was to propose publicly.
He was authorized to promise Publius Scipio privately a large sum of money and the surrender of his son, whom the king had taken prisoner in Greece as he was sailing from Chalcis to Demetrias. This son was the Scipio who afterwards took and destroyed Carthage, and was the second to bear the name of Scipio Africanus. He was the son of Paullus, who conquered Perseus, king of Macedonia, and of Scipio's daughter, and had been adopted by Scipio. The Scipios in council gave this answer to Heraclides, "If Antiochus wishes peace he must surrender not only the cities of Ionia and Aeolia, but all of Asia this side of Mount Taurus, and pay the whole cost of the war incurred on his account."
Privately Publius said to Heraclides, "If Antiochus had offered these conditions while he still held the Chersonesus and Lysimacheia they would have been gladly accepted; perhaps so if he were only still guarding the passage of the Hellespont. But now that we have crossed in safety and have not merely bridled the horse (as the saying is), but mounted him, we cannot consent to such light conditions. I thank the king for his proposal and shall thank him still more after receiving my son. I will repay him now with good advice, that he accept the terms offered instead of waiting for severer ones."
 After this conference Publius was taken sick and withdrew to Elaea, leaving Gnaeus Domitius as his brother's counselor. Antiochus thinking, as Philip of Macedonia did, that nothing worse than these terms could befall him if he were vanquished in war, drew his forces together near the plain of Thyatira not far from the enemy, and sent Scipio's son to him at Elaea.
Scipio advised those who brought his son that Antiochus should not fight until he himself should return to the army. Antiochus, acting on this advice, transferred his camp to Mount Sipylus and fortified it with a strong wall. He also interposed the river Phrygius between himself and the enemy, so that he should not be compelled to fight against his will.
Domitius, however, in a spirit of ambition, wanted to decide the war himself. So he boldly crossed the river and established a camp at a distance of 3½ kilometers from Antiochus. Four days in succession they both drew up their forces in front of their own fortifications, but neither of them began a battle.
On the fifth day Domitius did the same again and haughtily advanced. As Antiochus did not meet him he moved his camp nearer. After an interval of one day he announced by herald in the hearing of the enemy that he would fight Antiochus on the following day whether he was willing or not. The latter was perplexed and again changed his mind. Although he would have ventured heretofore only to make a stand under the wall or to repel the enemy from the wall, till Scipio should regain his health, he now thought that with superior numbers it would be disgraceful to decline an engagement. So he prepared for battle.