How did the Greek respond to the threat from Persia during the Persian war

The city-states of southern and central mainland Greece held a conference and resolved to oppose th Persian demands for submission. They also sent envoys to the western Greek cities in Sicily and the islands soliciting support. They elected Sparta to command on land and sea, and patched over standing disputes between the cities, at least for the time being.

The Spartans and Athenians sent a force of 100 ships and 10,000 warriors to the pass at Delphi to try to head off a Persian advance, but finding that thee pass could be easily outflanked by an inland route, soon abandoned it.

It was obvious that the key factor was the dominant Persian fleet, which could threaten all of the southern city-states one by one, which as a consequence kept their armies at home defending their cities, and these cities could be defeated one by one. So in order to be able to concentrate their land forces against the Persian army they had to get rid of the threat of the Persian fleet.

They resolved to block the Persian army at the pass of Thermopylai and so force the Persians into a sea battle to turn the position, and the sea battle would be in a narrow passage at Artemesion wher the larger and more numerous Persian ships could be matched.

The sea battle faied and the blocking force was withdrawn from the pass, so they made a second attempt in the similarly narrow waters at Salamis, which suceeded. The depleted Persian fleet was withdrawn to Asia and half the Persian army was sent home as there was not enough food in Greece to support it during the winter now that the Persian fleet could no lomger protect the resupply ships from Asia.

This evened things up. With the threat to their cities gone, the Greek cities sent their armies to join up in the spring and defeat the remaining Persian force and its Greek allies at Plataia.

Of course, after they had defeated the Persians who went home, the cities went back to fighting each other.