The Battle of Thermopylae was a battle of the Lamian war fought 323 BC between the Athenian and Greek armies in the pass of Thermopylae.

When Antipater heard about the Greek revolt, he sent messengers to Craterus and Philotas who were in Asia with an army of over 10,000 soldiers, to come to his aid. But receiving news of the progress of the rebellion and realizing that he could not wait for his reinforcements to arrive he marched south to Thessaly with 13,000 foot soldiers and 600 horsemen, while he left Sippas in command of Macedon. But the Thessalians who in the beginning supported Macedon changed sides to the Greek alliance and Leosthenes forces, occupying the passes of Thermopylae significantly outnumbered the Macedonians. Antipater was defeated and since he could not retreat because the Greeks had more cavalry than him he shut himself in the city of Lamia where he was besieged, giving the war its name.