What battle formation did the Spartans use to fight the Persians at thermopylae?

At the Battle of Thermopylae, the Spartans employed the phalanx formation, a tightly packed arrangement of heavily armed infantry soldiers known as hoplites. This formation allowed them to create a strong defensive front, using overlapping shields and long spears to maximize their combat effectiveness against the numerically superior Persian forces. The narrow pass of Thermopylae further enhanced the advantages of the phalanx, as it limited the ability of the Persians to fully exploit their numbers.