How were the Greek defenses at Thermopylae and Artemisium connected?

During the second Persian invasion of Greece in 480 BCE, the Greek defenses at Thermopylae and Artemisium were strategically linked as a unified holding operation intended to halt and damage the advancing Persian forces.12

The two positions were geographically close enough that the respective commanders—the Spartan king Leonidas at the land pass and Eurybiades at the naval station—maintained active communication to coordinate their efforts and stay informed of each other's status. The land force at Thermopylae aimed to block the southward advance of the Persian army into Attica and Boeotia, while the fleet at Artemisium sought to engage the Persian navy to prevent it from outflanking the land position or landing troops behind it.123

This coordinated defense lasted for three days. The connection between the two fronts was severed only when the fall of Thermopylae became known, prompting the Greek fleet to withdraw southward to the straits of Salamis.14