At the start of the Persian Invasion, there were 300000 persians (or more, none is sure) and Athenas ordered a messenger to call help to Sparta, Sparta answered, but with only 300 soldiers in case of the persian invasion not being true. There were 7000 greeks soldiers and 300 spartans or even 900, as a guy wrote somewhere in the forum. After days of battle,, someone told the persians a route to flank the greeks, Leonidas knew it before this, so sended soldiers from a nearby city to protect it, but they feared a attack on their city and retreated to the city.
Leonidas told to the greeks that they can return home, many did it, but the thebans(I think) stayed there and helped the spartans, they lose the battle.
Also, the people forgot about a Admiral that said to Athenas to invest on their naval, but none gave a **** to it, so he told a false story about a naval spartan attack, so Athenas invested on naval. In the greco-persian wars, this admiral protected the greek ground forces on the Thermopylae from the flanking of persians (they would transport persian forces by sea and flank the greeks).
Leonidas told to the greeks that they can return home, many did it, but the thebans(I think) stayed there and helped the spartans, they lose the battle.
Also, the people forgot about a Admiral that said to Athenas to invest on their naval, but none gave a **** to it, so he told a false story about a naval spartan attack, so Athenas invested on naval. In the greco-persian wars, this admiral protected the greek ground forces on the Thermopylae from the flanking of persians (they would transport persian forces by sea and flank the greeks).