Why was the battle of artemisium so important

The southern Greek city-states facing the Persian invasion in 480 BCE were faced with the prospect of amphibious attacks by the Persian fleet on their cities. They kept their armies at home to protect themselves, so giving the Persian army a walkover, able to pick them off one at a time.

The Greek strategy was to destroy the Persian fleet to both lift this threat to allow their armies to come out and combine to defeat the Persian army, and also to expose the Persian sea supply line on which the Persian army depended, as Greece was too poor a country to support them.

They at first sent a land blocking force and fleet from Sparta and Athens to the pass at Tempe in northern Greece, but withdrew it when they found that the inland route would easily bypass it. They then sent a small force to the narrow pass at Thermopylai with the fleet positioned in the strait of Artemesion beside it to force the Persian fleet to try to turn the land block by sea, so precipitating a sea battle in narrow waters which would favour the Greek fleet tactically.

The fleets engaged for three days and the Greek fleet had the worst of it and withdrew to Salamis to try again. The Thermopylai land force was therefore withdrawn, the Spartans sacrificing themselves to hold the pass as long as possible to let them get away.

A good plan which failed because the odds at sea were too great in both ship size and numbers. They had to try again with a better strategy required – one which split the Persian fleet to even the odds.

Aftermath:

The Greeks then ran a this-time successful re-run battle at Salamis, splitting the Persian fleet and catching it spread out thinly in the narrow waters around Psyttaleia Island. This loss of sea dominance left the Persians undersupplied for the winter as their supply ships could not now be protected by the defeated navy which withdrew to Asia Minor, and they had to send half of their army home.

This levelled up the odds and the following spring the Greek cities sent out their forces to combine, the armies defeating the weakened Persian army and its Greek allies at Plataia in central Greece, and the Greek fleet destroying the residue of the Persian fleet holed up at Mycale in Asia Minor.