The Battle of the Eurymedon took place between the Athenian-led Delian League and Persia on the Eurymedon River in Pamphylia in Asia Minor. The specific date is unknown, but it was between 470 BC and 466 BC.
Asia Minor campaign
The Greeks, according to Thucydides led by Cimon of Athens, actually defeated the Persians in two separate battles on the same day, first at sea and later on land. The prelude of the battle was a campaign the Delian league launched against the Persians in Asia Minor in order to secure it's possessions in the Aegean sea from possible Persian aggression. Two descriptions of the battle are available. Plutarch and Diodorus Siculus. They both agree that Athenian general Cimon led 250 Athenian ships against the Persians in Asia Minor. According to Diodorus the 250 ships were joined by 100 more from Ionia and other members of the Delian league. The Greek cities near the coast of Caria surrendered without resistance, but the cities with mixed Greek and Persian culture and language resisted and were besieged by Cimon. The city that held out the longest was the Greek-speaking Fasilida. According to Plutarch the contingent in the Athenian army from Chios who were long-standing friends of the Fasilides, shot arrows with written messages over the city walls asking their friends to submit. The inhabitants of the city accepted and after offering 10 talents in tribute to the Delian League, they joined the Athenians' campaign. Before long, Cimon had also subdued the majority of Lycia cities, adding them to the League.
After bringing the coastal cities under his control, Cimon moved in on the Persian navy with his fleet near Eurymedon River. Two accounts of the battle have been preserved, one by Diodorus and one by Plutarch. Both writers mention Tithrafstes, as Persian naval commander. Tithrafstes was an illegitimate son of king Xerxes. Supreme commander of the ground forces was Ferendatis, but according to Plutarch the most influential leader was Ariomandes. Plutarch says Ariomandes with the bulk of the Persian naval force lay anchored near the Eurymedon River, waiting to be reinforced by another 80 Phoenician ships from Cyprus with the Persian infantry camped nearby. Cimon attacked Ariomande's fleet before the reinforcements could arrive and in the beginning the Persians tried to pull away, but were soon forced to give battle. Plutarch mentions two different accounts of the number of Persian ships; according to Ephorus the fleet consisted of 350 ships. The Athenians won the sea engagement, capturing many of the Persian ships. The surviving crews and soldiers from the Persian ships joined the troops on land. Cimon and his forces then disembarked and made a night attack at their camp, fighting a hard-fought battle with both sides suffering severe casualties before finally winning, taking many Persian prisoners. After claiming this victory, the Greeks went after the Phoenician reinforcement ships which in the meantime had fled to Hydra island, not knowing the outcome of the hostilities. Cimon took them by surprise and destroyed most of the ships.
Diodorus Siculus on the other hand, gives us a quite different account of the events. He agrees on the fact that it was Cimon who first attacked the Persian navy, but locates the battle near Cyprus instead of by the Eurymedon river. After winning the sea battle the Greeks pursued the fleeing Persian forces to Cyprus, where the Persians abandoned their ships and took refuge in the countryside. This way Cimon captured a handful of Persian ships which he manned with Athenians dressed in Persian uniforms. In this disguise Cimon led his men in the captured ships up the Eurymedon river where the unsuspecting Persians let them into their camp. In the surprise attack that followed, the Greeks won an easy victory, killing the Persian general Ferendatis in the fight. Of the two versions Plutarch's account is generally seen as more believable, because it shares important details with the short account given by Thucydides, which is considered the most accurate source for the event, since Thucydides' written text is dated closer to the event (some decades after, while all other accounts were written several centuries later).
The battle proved that the Athenian-led Delian League could fulfill its objectives. The Persian fleet was no longer a real threat in the Aegean Sea. A year after the battle, Cimon attacked and defeated the remaining Persian forces in the Thracian peninsula. This victory secured the Greek fleet's definite control of the Aegean sea and left the Athenians free to pursue their broader political motives; making their Delian League allies tributary states in an Athenian empire and challenging for the supremacy in the Greek world. This situation lasted until the destruction of the Athenian expeditionary force in Egypt, possibly between 460 BC - 456 BC, an event that contributed to the reemergence of Persia as a major naval power in eastern Mediterranean.
Olmstead A.T., History of the Persian Empire, 1948, Chicago
 for Diodorus "Library"
 for Thucydides "Histories"
 for Plutarch's account on Cimon
These by the streams of fam'd Eurymedon
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