What countries were involved in the thermopylae battle?

The Battle of Thermopylae - Order of battle :

Spartans 300

Lacedaemonians/Perioeci 900

Spartan helots 900

Mantineans 500

(other Peloponnesians sent with Leonidas)

Tegeans 500

Arcadian Orchomenos 120

Other Arcadians 1,000

Corinthians 400

Phlians 200

Mycenaeans 80

Total Peloponnesians 3,100

Thespians (The Sacred Band) 700

Malians - 1,000

Thebans 400 400

Phocians 1,000 1,000

Opuntian Locrians

[Numbers subject to revision.]