Why did the battle of salamis took place

Persia invaded peninsular Greece to incorporate it within its empire in an attempt to bring peace to the Greek world and so stop Greek wars spilling over into its empire. Its force included a powerful navy which threatened the Greek cities, most of which were located on the coast. As a result of this threat, the Greek city-states kept their armies at home to defend their cities, and the Persians were able to use their army to pick off the cities one at a time.

The southern Greek cities determined to destroy the Persian fleet to remove this threat, so that they could then concentrate their armies against the Persian army. They first tried to do this by blocking the pass at Thermopylai to force the Persians to bypass it with a naval outflanking move through the strait of Artemesion nearby, and the combined Greek fleet lay in wait to defeat the Persian fleet. The Greek fleet lost, so it retired to the strait at Salamis to regroup and try again. Here they defeated the Persian fleet.

The result was that the Persians had to send half their army home, as they could not feed it as their resupply fleet could not supply it with the naval protection gone, and the Greeks were able to send out their armies to concentrate at Plataia the following spring with the amphibious threat to their cities gone also. The Greek coalition won the battle of Plataia, and the Persians went home.