There is nothing wrong with a spec historical drama, except that it’s too expensive and unless it’s a war picture about the jaw-dropping bravery of soldiers that A-list actors can play, no one knows how to market it.
There are notable exceptions that follow these rules designed to give your thirst for history impact on the page.
Keep your scope limited. The King’s Speech isn’t a biopic of the entire life of Colin Firth. It’s tempting with history to put in ALL of it. Start on a small scale, one exciting emotional event, one exciting emotional person.
Reverse your angle. History puts you up against a wall with story because mostly, we know how it’s going to turn out. Reporting events is not as important as following along the emotional journey of the person who lived it.
Accuracy is not your friend. Combine characters who have like functions, fudge the timeline for drama, embroider a fact to raise the stakes. Or lots of them. Like Argo did.
Pedestals make dull characters. Historical heroes and heroines are still people. They piss off their friends and make bad decisions and fall in love with the wrong person. Don’t be shy about showing them at less than their Sunday best.