Ten years had passed since a smaller army of Athenians defeated the Persians at Marathon. Remember the story? Outnumbered during the late summer of 490 BCE, the Greeks fought with courage and resolve. After the battle - according to legend - a messenger ran the entire distance from Marathon to Athens. After he reported an Athenian victory, it is said the runner dropped dead of exhaustion.
Marathon was much more than a victory. It showed the Persians could be defeated. But Xerxes, who was crown prince in 490, was the Great King in 480. He planned to finish what his father, Darius I, had started: to subjugate the Greek city-states, including Athens and Sparta.
Ordering his troops to construct a "boat bridge" - so the army, and all of its supplies and supporting personnel, could cross the waters of the Hellespont (now known as the Dardanelles) on foot - Xerxes set out to defeat the Greek city-states. Who could resist such a formidable ruler?
The Great King was on the move. But his would-be Greek subjects were experiencing life under a new political reality. Democracy was in its formative years and, if the Greeks became part of the Persian empire, they would lose their ability to be free. Not just unable to govern themselves, free Greeks would then become Persian subjects.
The early years of democracy, of course, were set against a background of slavery, even in Greece. Spartans, for example, had their own slaves - called Helots. And women, especially in Athens, had unequal rights. But if the Persian army were to rout the Greek city-states, the concept of democracy - where people have the right to govern themselves - would be replaced with subservience to the Persian ruler.
Xerxes wanted to avenge his empire’s loss at Marathon. The Greeks had defeated the Persian army once before. Could they do so again?