The battle of Thermopylae was fought between the Greeks (Sparta and Athens) and the Persians. The Persian leader, Xerxes, wanted revenge on the Greeks for the destruction of Sardis, a Persian city, so he led the Persian army of up to 300,000 men to invade Greece (which was not known as Greece at the time, just as separate city-states). The Spartan leader, Leonidas, learned of the attack and gathered 7,000 men (only those who had fathered a son), to meet the Persians.
The Spartan Soldiers all had been trained since a very young age how to kill a man. Their society made all men when they turned 20 join the army. They were expert fighters and intelligent scholars. They’re armor was made of bronze and woods and was much better than the weapons of the Persians.Woman were also trained in combat, but not for war. Their society believed that woman should be strong so they would have strong and healthy children. If a baby was not believed to be healthy or had a physical ailment, the baby would be killed. The Spartans were also very religious. The Oracle of Delphi was the most important shrine of Greece. Leonidas consulted the Oracle before he went into battle.
The Persian Empire was very large and strong.Persian soldiers were paid by the government to be full-time soldiers. The royal Persian bodyguards, the Immortals, were very highly skilled and were called immortals because if any member fell sick or died, he was immediately replaced. The number was always at exactly 10,000. The Persians also faced many internal problems. As the empire grew larger, it became difficult to manage.
The first day of the battle is known as the Battle of Marathon. It was there that the Athens had their first victory. The 20,000 Persians that had come that day waited for the Athenians, but the Athenians were smart and they knew that attacking the Persians would be a mistake. The Persians became tired of waiting, so they decided to sailed south to attack