With his plan under threat, Themistocles was forced to take the initiative. By night he sent a messenger to the Persian king, Xerxes, informing him that the Greeks intended to flee. Unless he acted now, Xerxes would lose the opportunity to defeat the Greeks in one fell swoop. The Persian king took the bait.
As dawn broke Xerxes sat upon his portable throne overlooking the sea, and prepared to relish his victory over the defiant Greeks. However, as his vast armada sailed into the narrow straits between Salamis and the coast, they were met not by a fleet in disarray, but a well-ordered line of triremes, packed with Greek crewmen singing battle songs. Themistocles had forced them to fight.
In the battle that followed, the Persian armada was devastated. The Greeks lost 40 ships, the Persians 200. Unable to keep his land army supplied Xerxes was forced to flee back to his empire, parts of which, encouraged by the Greeks' success, had already started to rebel.
The victory at Salamis has often been described as one of the greatest naval victories of all time, and a key event that shaped the whole future of European civilization.
How Salamis was remembered - Aeshylus' The Persians
Themistocles' message to Xerxes