How were the Greeks able to defeat the Persian fleet

The Greeks recognised that their only hope against the more numerous and heavier Persian ships was to get them in narrow waters where they could be outmanoeuvred by the more agile Greek ships, whose principal weapon was the ship’s ram. They tried this first in the strait at Artemesion where the stand at the Thermopylai pass forced the Persians to try to turn the position by sea, but the battle was lost.

They retired to the strait between Salamis island and Athens to try again. This was a better location, as the Persian fleet had to split in two narrow columns to get through the channel on each side of the island of Psyttalia, and exposed their flanks to the waiting Greek ships ramming tactics.

The balance of forces was also much helped by further debilitating the Persian fleet – Greek agents persuaded the Persians that the Greek fleet would not stand for battle, but escape through the back passage past Megara. The Persians sent the Egyptian third of their fleet around to cover this, and so the numbers of ships on both sides were evened.

They also persuaded the Persians that the Greeks might surrender, so their ships sat at oars all night outside the bay in a swell waiting and were exhausted by the time they closed in for battle the following day.

King Xerxes sat on a headland to watch the battle. He had need to give his supervision as his remaining ships were from Phoenicia and the Greek cities within his empire, and so were not all that enthusiastic about fighting for Persia anyway.

So what appeared to be a dominant Persian fleet was in fact reduced in numbers, fitness for battle and enthusiasm for the cause, and caught in a disadvantaged tactical deployment in the narrow waters.