Might I suggest heading to your local Community College and taking a course on the History of Civilization to 1645?
There was plenty of blackmail, extortion and backstabbing during the Roman Empire.
I actually watched 300 in my history class because my professor was a young guy, "hadn't seen it yet, and wanted to find some bullshit reason to show it in class". So we watched it and he would stop here and there in order to explain how and why certain events took place. Essentially, the battle in and of itself was the only thing that is documented to have happened.