The document summarizes key events in the first and second Persian Wars between Greece and Persia. It notes that in the first war, the Athenians defeated the Persians at the Battle of Marathon. However, in the second war, Xerxes sought revenge for his father Darius and wanted to conquer Greece. Only 300 Spartans fought at the Battle of Thermopylae against the massive Persian army of 2.7 million men, but they were betrayed by the Greek Ephialtes and all were killed, allowing the Persians to advance further into Greece.