I've been dedicating a lot of my recent RPG creativity to writing historical gaming scenarios. I've written three Lovecraftian horror scenarios set during the American Civil War (with a fourth in progress), as well as another couple of scenarios set during the standard Call of Cthulhu period of the 1920's that include strong real-world historical elements. I've also been researching the Black Death in 1340's Europe, ideally for a future Red Markets-related project. If you want to listen to some of my scenarios, I'm running them here on Technical Difficulties (check out He Calls Me by the Thunder, part 1 and part 2), as well as for Role Playing Public Radio.
I also really love reading and playing historically-focused RPG scenarios, like Caleb Stokes's No Security scenarios set during the Great Depression, and the Trail of Cthulhu World War I collection Dulce et Decorum Est from Pelgrane Press.
I figured I'd share a few of my thoughts and tips about designing historical scenarios, since I've been thinking about it so much recently.
1. For me, the most fun thing about historical scenarios is getting to explore a new time and place, to imagine how people living in that place would deal with strange and dangerous situations differently than someone living in our modern world. I always play up the unique historical conditions of a scenario, even as I'm mixing in fantastical or supernatural elements. How might a Lovecraftian monstrosity affect an Antebellum slave plantation? How would a 1920's radical socialist newspaper deal with a malevolent sorcerer?
2. I recommend writing pre-generated characters for most historical scenarios. I don't want to force my players to do a bunch of their own historical research just to make up appropriate PCs. So I'll write characters that fit an appropriate archetype: the wounded artillery officer, the corrupt militia trooper, the crusading field nurse. But I also make sure to leave the pregens vague enough that each player can invest their own details into their character's personality, to make it their own.
3. When I'm researching for a game, I start broadly and then get more specific. A prominent historical event can be the seed of a scenario plot, like the Gettysburg Address or the Missouri Mormon Wars. I'll cruise Wikipedia or read a general history to get broad ideas. Then to develop the scenario, I'll dive into the detailed facts of the event and let that shape my plot, like how the black workmen on the Gettysburg National Cemetery project were surprisingly well-paid, and how Lincoln was getting sick while he was giving his speech. Having loads of details adds a lot to the players' sense of immersion.
4. That said, I have to resist the urge to cram every single tidbit in. Remember, we're writing games, not lectures. The main focus needs to remain on the characters' choices and actions, not just on the set dressing. Make sure that the details you do emphasize are ones that the PCs can use to inform their actions, so that they feel more like they're embodying real people from the era. The design of the Gettysburg courthouse probably doesn't matter, but the person playing the war widow might like to know a lot about the traditions of mourning dress.
5. Make sure that you let the actual play at the table be as free and open as you would in any game. Don't pull a "Stop having fun, guys!" on your players, just because they're doing something that doesn't quite make historical sense. Maybe gently remind them of how a particular historical fact might guide their behavior, but don't be a stickler about it. Remember, nobody's getting graded at the end of this.
Those are just a few tips. I might revisit this subject again in the future, to talk more theoretically about how to use historical games to explore big themes, or how to take ideas from historical research and use them in other genres like fantasy and science fiction. Let us know if you you find this sort of thing interesting! I hope I'm not the only one. :)