The battle of Eurymedon (or Side) of 190 B.C. was one of two naval battles that marked a turning point in that year's fighting in the war between Rome and Antiochus III. After suffering a naval defeat at Corycus in the previous year, Antiochus had reinforced his fleet in western Asia Minor, and ordered the great Punic general Hannibal to raise a second fleet in Phoenicia.
Antiochus faced a coalition of Rome, Rhodes and Pergamum. His best hope of a naval victory was to divide the allied fleet, and defeat them in detail. Only the first part of this plan would end in success. The allies were aware of the danger from Hannibal, but they could not afford to concentrate all of their ships in the threatened area, for the main Roman army under the Scipio brothers was marching towards the Hellespont, where it would need naval support. Eumenes of Pergamum and his fleet thus had to be posted in the northern Aegean, to support the army. When news reached the Roman and Rhodian fleets that Hannibal was on his way, the Rhodian fleet under Eudamas was sent east to deal with the new threat.
Unfortunately for him, Hannibal’s fleet was designed to defeat the Romans, not the Rhodians. The Romans relied on the quality of their infantry to win their naval battles, grappling and boarding enemy ships. To cope with this tactic Hannibal had constructed a fleet of large warships – his 47 decked ships included three hepteres, four hexeres, thirty penteres and tetreres and ten trieres. In contrast the Rhodian fleet contained 32 tetreres and 4 trieres, and they had no intention of fighting boarding actions.
Instead the resulting battle depended on the skills of the ship’s crews and captains, and here the Rhodians had the advantage. Although Hannibal, on the Syrian left, did well in the early fighting, Apollonius, on the Syrian right, was soon in trouble and had to call for help. As ships responded to this call, Hannibal also found his wing in trouble, and soon both wings of the Syrian fleet were forced to flee.
The exact number of Syrian ships lost is unclear. Livy reports that twenty were undamaged, and mentions two that were lost. At the very least another twenty five much have been damaged, and Hannibal’s fleet was eliminated from the fighting. Eudamas and part of the Rhodian fleet was free to rejoin the main Roman fleet in time to take part in the decisive naval battle of the war, at Myonnesus.