A Greek force of approximately 7,000 men marched north to block the pass in the middle of 480 BC. The Persian army, alleged by the ancient sources to have numbered over one million, but today considered to have been much smaller (various figures are given by scholars, ranging between about 100,000 and 150,000), arrived at the pass in late August or early September. The vastly outnumbered Greeks held off the Persians for seven days (including three of battle) before the rear - guard was annihilated in one of history 's most famous last stands. During two full days of battle, the small force led by Leonidas blocked the only road by which the massive Persian army could pass. After the second day, a local resident named Ephialtes betrayed the Greeks by revealing that a small path led behind the Greek lines. Leonidas, aware that his force was being outflanked, dismissed the bulk of the Greek army and remained to guard their retreat with 300 Spartans, 700 Thespians, and 400 Thebans, fighting to the death.
how many persian soldiers were at the battle of thermopylae
about 100,000 and 150,000