During two full days of battle, the small force led by King Leonidas I of Sparta blocked the only road by which the massive Persian army could pass. After the second day of battle, a local resident named Ephialtes betrayed the Greeks by revealing a small path that led behind the Greek lines. Aware that his force was being outflanked, Leonidas dismissed the bulk of the Greek army, and remained to guard the rear with 300 Spartans, 700 Thespians (who refused to leave), 400 Thebans and perhaps a few hundred others. Most of them were killed.