Approximately 7,000 Greek soldiers fought at Thermopylae in 480 BC. This force was a coalition from several Greek city-states, led by King Leonidas I of Sparta, and included about 300 Spartans among its ranks.
The Greeks chose Thermopylae because its narrow coastal pass limited the advantage of the much larger Persian army. The position allowed heavily armed Greek hoplites to fight in a tight formation, using shields and spears to block the route into central Greece.
The figure of 7,000 refers to the force that initially assembled at the pass, not the smaller group that made the final stand. After the Persians discovered a mountain path around the Greek position, most of the army withdrew. Leonidas remained with the 300 Spartans, 700 Thespians, and other defenders, including Theban troops according to ancient accounts.
Popular retellings often suggest that only 300 Greeks fought at Thermopylae. The 300 Spartans became the battle's most famous symbol, but they were part of a broader Greek force of roughly 7,000 men.