I don't think the dialogue of Frank Miller's FICTIONAL graphic novel was taken directly from historical events/books.. (correct me if I'm wrong though)
The plot was loosely based off historical events, and I stress the term loosely. I doubt that in the battle of thermopylae the Persians brought in guys with blades as arms and ogres locked up in chains to unleash on the Spartans. I also find it tough to believe that the Greek traitor Ephialtes was really the hunchback of Notre Dame back in 480 BC. So ya, I personally think there could have been some improvemetns since it is a fictional film, not a history documentary.
several lines in there were straight out of the history books. as for the fictional characters? yeah. those obviously were NOT based off history. but the fact that someone did lead the persians around the side to attack is 100% true. and basically the overall storyline and how they attacked and what the persians sent to them is true. the rest was just added to make it seem more exciting. thats frank miller's additions.
there were other things that were not so real. in history they wore armor. but the battle stances were 100% accurate as well. so was the way they were brought up. lets face it. the movie wasnt 100% accurate. it was based off Miller's graphic novel which was fiction, but based off truth. if you didnt like the fake parts of the movie then ok. but the plot, the storyline, thats all history from truth in the battle. if you didnt like that,t hen you went to see the wrong film. im mostly scottish. so i loved watching braveheart (i just keep going to that because its my favorite movie, and i did a LOT of studying on it).
ill still pk u