Spartans at the gates of Thermopylae

War History Online has this:

Zac Snyder’s movie, 300, came under fire for its fanciful retelling of the Battle of Thermopylae. Nevertheless, he stuck to the gist of what actually happened (pretty much).
Back then, Persia was the superpower, while Greece was just a collection of city-states. Persia had invaded Greece in 492 BC, but was kicked out two years later at the Battle of Marathon, commemorated today by the Olympic flame.
Understandably upset, the Persians under Xerxes I tried again in August of 480 BC. The Athenians tried to block the Persian navy at the Straits of Artemisium, but another Persian force of perhaps a hundred thousand men landed at Thermopylae Pass, which is where King Leonidas I of Sparta comes in.
Taking three hundred of his royal bodyguard with him, Leonidas made his way to Thermopylae. By the time he got there, in mid-August, he had about seven thousand men from other city-states… all of whom wore armor.
The Persians sent Leonidas an ambassador, urging him to surrender. He refused, so the Persian army dug in. Five days later, on 20 August, Xerxes ordered his archers to fire at the Greeks. Given the distance, as well as the bronze shields and helmets the Greeks wore, it did no good. So Xerxes ordered an all-out attack by the cavalry. The Greeks retreated and let them pass. Once deep within their lines, however, they closed ranks and cut the Persians down. Thus ended day one with few Greek losses.

Rico says yet another war (pre-antibiotics and pre-surgery) he's glad he missed...