I need facts about Thermopylae anything will work…. thanks anyone who posts really helpful

The Greeks had determined that, due to the threat of the Persian fleet and its amphibious capacity to attack and defeat the independent cities one by one, and as it also protected the Persian sea supply lines, that they had to defeat that fleet. As it was superior in size and numbers, they had to catch it in narrow waters to neutralise its superiority, so they set up a small blocking force in the narrow pass at Thermopylai to hold up the Persian army plus its accompanying fleet in the narrow strait nearby. The blocking force had to hold on long enough for the Greek fleet to defeat the Persian fleet. After three days of naval engagements, the Greek fleet came off worst and withdrew to Salamis near Athens.

The 8,000 Greek force at Thermopylai held on for two days against the 180,000 strong Persian army, while the naval battle went on, and then had to hang on for a third day for the deciding naval battle. Meanwhile the Persians had sent an outflanking force to attack the pass from the rear. Warned that this was happening the Greek commander Leonidas sent off most of his force to seek protection in the walls of friendly cities, and so that the Persian cavalry could not rush through and catch them in the open, held the pass with his force of 2400 Spartans (300 hoplite infantry and 2,100 helot light infantry), 700 Thespians who demanded to stay, and 400 Thebans he forced to stay because Thebes was suspected of secretly going over to the Persians. After the main body had got away, the outflanking Persian force joined in the fight, and the attack from both sides overwhelmed the remaining defenders.

With the failure of the naval battle, this sacrifice at Thermopylai was unfortunately without any military effect. It did however provide a morale boost and a lesson that reinforced the Marathon experience – the Persian infantry could not stand up to armoured warriors without their cavalry.

The Greek fleet subsequently defeated the Persian fleet at Salamis. The Persian supply fleet was now open to interdiction, and faced with winter in a poor countryside, Xerxes had to take half his army home, and the following year, the other half, with its Greek allies, had to face the full forces of the southern Greek states, as without the threat of amphibious invasion they could leave their cities and concentrate at Plataia. The depleted Persian ground forces were defeated at Plataia and the remaining rump of their naval forces at Mykale.