The movie is historical fiction really based on a graphic novel. Obvious blaring historical inaccuracies: (Sparta had 2 kings, There were around five thousand Greeks at Thermopylae , 700 Thespians aided the 300 Greeks, No mention that at the same time the Greek fleets battled the Persian navy and inflicted heavy casualties). Also I would like to know, did they start with 300 spartan, or did they die as 300? Because all things considered, several Spartans were killed during the battle.
In the end it really doesn't matter. I'm surprised no one really realizes this, but it's when you really look at the movie, the entire thing wreaks of bias. Who narrates the film? Dilios, a Spartan. Think about it he is retelling the story throughout. You aren't witnessing the actual events, you are taking a journey through a story told by a good story teller. Thats why the 150,000 Persians became a million. That is why Persians are "monstrous", and the Spartans are heroes. Of course only the Spartans would appear as courageous and the rest of the Greeks cowardly. The only Spartan depicted as being deformed was a traitor. It's a movie about perspective, with some really cool ****ing battle scenes, and is in no way a "documentary". As the director said, He(Dillios) knows how to tell a story without throwing in facts to make it boring.