King Leonidas .
The "300" were Spartan hoplite soldiers led by their king Leonidas who fought at the battle of Thermopylae .
King Leonidas. He led the battle of Thermopylae with 300 Spartans. His people killed 20000 Persians.
There was a coalition of Greek forces numbering about 4000 at Thermopylae. The coalition was led by King Leonidas and 300 Spartans.
It was roughly 300 Spartans - King Leonidas I and his personal bodyguards.
Xerxes I.
Back in ancient times it was the place of battle between the Spartans led by Leonidas and the Persians led by Xerxes. The modern-day location is simply Thermopylae, Greece. Hope that helps. :-)
Leonidas
Their king, Xerxes I.
King Xerxes I.
If by spy, you mean the person who betrayed the Spartans, that would be Ephialtes of Trachis.
The Spartans and the Persians
King Leonidas