Who was the strategist behind the Thermopylae-Artemisium defense

To block the pass to provoke a sea battle. The Persian fleet was a threat to the Greek cities which kept their armies defensively at home. If the Persian fleet was destroyed, the Greek city armies could come out and unite to face the Persian army. Also the Persian supply fleet carrying food and forage for the army from Asia Minor would be exposed and the army could not be sustained in such a poor countryside as Greece.

The Persian strategy was to threaten the cities with its navy and so stop the Greek city land forces uniting. They could then pick the cities off one at a time – easy pickings. Athens had to be abandoned as a starter.

Unfortunately for the Greeks their attempt on the sea battle of Artemesion in the strait next to Thermopylai was lost, so the Thermopylai force now had no task and was withdrawn. The Greeks tried again at Salamis near Athens and won. The Persians could not feed themselves without the supply fleet from Asia Minor, and had to send half their army home. This made it easier for the Greek armies, which could now combine with the amphibious threat to their cities gone, to defeat the Persian army at Plataia the following spring.