Thermopylai was a battle in the Persian War.
5th Century BCE - 480 BCE to be precise, and Thermopylae was not a war but rather a small battle in a 50-year war.
The answer is the Persian war.
It was not a war, it was three days of holding the pass and then withdrawing.
They joined the spartans and won the war
The Persian war ended Persian expansion to the west. Thermopylae was a minor tactical delaying action which failed.
Thermopylae
Xerxes I.
stagey*
Persians.
The Battle of Thermopylae took place in the second of the two Persian Wars, also known more recently as the Greco-Persian Wars.
The narrow coastal pass of Thermopylae . August or September 480 BC
The battle of Thermopylae.