Battle of Thermopylae (480 B.C.)
Following the Athenian victory at Marathon, Persia still had it's sights on Greece. When King Xerxes took power in Persia he began to mass both naval and ground forces for an assault on mainland Greece. Sparta, along with Athens and 29 other city-states united to defend Greece from a possible invasion. The Athenians contributed 200 ships to the Spartan fleet as ordered by the Athenian General Thermistocles. He believed that the war would be fought mostly at sea.
When the Persians entered Greece in the north, many northern city-states laid down their arms to them because the well armed city-states to the south chose not to meet Xerxes armies in the area. While the Greek powers argued over where to fight the Persians, the final decision was made for an expeditionary force to meet the Persians at Thermopylae pass.
The Greeks had a force of 10,000 men lead by King Leonidas of Sparta. When the Persian army met the expeditonary force, they retreated back to Thermopylae pass where they would make there stand using the phalanx tactic that had one the battle at Marathon. The Greek force managed to slaughter the waves of Persians, it seemed that a victory was possible.However, a Greek traitor named Ephialtes informed Xerxes of an alternate route that lead behind the Greek forces. When Leonidas was informed of this he released the other Greek forces except for his 300 Spartans. The heroic last stand of the Spartans was made to provide the other Greek forces the time to retreat back to Athens. The Battle ended with the Spartans being slaughtered and the Persians marching to Athens and razing it to the ground.Though the Persians one the battle at Thermopylae they didn't win the war. Although they destroyed Athens, the Athenians had already retreated to Salamis where their naval and ground forces waited. This next battle would be called the battle of Salamis.