Darius son XERXES I determined to conquer Greece. The Spartans organized an alliance of 30 cities to opose the invasion. The persians hordes met the Greeks in 480 BC at thermopylae. Using a narrow mountain pass to their advantage, the Greeks were able to hold off the invaders for three days before a traitor show the persians forces a way over the mountains, Upon the learning of the treachery, the spartan leader LEONIDAS ordered most of his troops to withdraw, he and 300 Spartans stayed behind and gave their lives to delay the persian army.
The war between Sparta and Athens began in 431 and lasted until 404, Sparta was the first to declare war to Athens, under Pericles leadership, all the Greeks even some Persians became involved in this war.