Thanks Perdogg for the ping. 7thson, it seems to me that there's a topic about this movie, somewhere, but I'm too lazy to find it. I've not seen it. The Spartan sacrifice at Thermopylae was a holding action which delayed the Persian advance a few days, and also it was a political maneuver to recover some prestige for Sparta, which a few years earlier had refused to participate in the defense of Greece, and saw Athens and other cities whip the Persians at the Battle of Marathon.
The Greeks had also withdrawn before the Persian navy, and the Persian army sacked Athens (the carved proclamation to the inhabitants to take refuge in the hills ahead of time actually still exists), then was lured into the Bay of Salamis by Themistocles' famous ruse. The Battle of Salamis eliminated the Persian navy, and led Xerxes the Persian king to retreat in a hurry to Anatolia.
The combined Greek armies, including that of Sparta, defeated the Persian land forces at Plataea.
During the Pelopponesian War the Spartans took money from the Persians, the latter being interested in the defeat and destruction of Athens and the divisions within Greece, with a view to keeping them out of Persia's business in Anatolia. The strategy worked, but Alexander the Great conquered Greece, and led a united Greek and Macedonian army across the Persian Empire.
Themistocles also wound up on the Persian payroll, ruling as a governor or something in one of the cities of Asia Minor which had been conquered by the Persians. His home city, Athens, had voted to ostracize him, and he was banished from the city for ten years. He never went back. If you're looking for a metaphor...
So, bottom line, from your post and others, is that the movie looks likes a good war/action flick and that should be the only reason to see it.
At the museum in Olympia, you can see a Persian helmet sent to the sanctuary by the Athenians from Marathon.
It's amazing.