War is an interesting thing when it comes to table top RPGs. I mean, if you thought a 6v6 fight could take a long time per round, imagine what happens when you upscale to hundreds and thousands vs. like numbers. Fortunately numerous systems have different ways to handle the chaos of the battle field in different abstract ways. But there is more to selling a war than just mechanics for the big fights. Today I want to talk about that.
Where Is Your Focus?
The first thing you have to answer when bringing a war to your table top game is where do you want your focus to be? Obviously around the PCs, but are we going to go in close and see how this war - and the horrors within - impact this group? How they make friends, fight, triumph, lose, despair, and otherwise make it through - hopefully but not guaranteed to be - in one piece? Or are we going to pull back and look at the war as a more grand thing where glory is won, heroes roam the battlefield, and your PCs become the stuff of legend?
There's nothing wrong with either. Some games, and groups, will gravitate to one or the other. Even the most munchkiny of D&D games can have some drama thrown in for good measure, and even the most drama-filled game of horror and sanity can do with giving the players a chance to feel like badass heroes.
The Close In Approach
Doing the close in approach is, in my opinion, easier mechanically but harder otherwise. It's easier mechanically because you basically don't have to worry about big battles too much. You can script the major battles to be wins, or losses - or depend on player results - and otherwise just narrate. Meanwhile you can build encounters for the more close knit group of PCs you have, keeping the focus on the squad level as they go through things.
The challenge here is that you need to let the players feel like they're part of the war. You need to make the players feel like they're not just getting their butt kicked in even if the war is going badly. And you need to find a way to sell the NPCs around the players so they make emotional connections with them. You're going in close for the drama of the moment, and you don't have that drama without meaningful connections to the NPCs that are also in the fray - regardless of what side of the war they're on.
Pyrric victories can be good here, as can losses that are out of the PCs hand in some way if you need a way for the PCs to win the small scale. Remember, there is a reason we have a saying "you won the battle but not the war" around. That said, take care to not make the PCs feel like they have no impact on the war at hand. Nothing is worse than just being an observer when you're supposed to be a main character.
The Far Back Approach
The Far Back Approach doesn't actually pull as far back as the name implies, but doesn't go in close for the knitty gritty either. Here we are basically pulling away from the consequences of war. You don't see friends die (and if you do it is a big deal) as much, and you don't get all the stress and doom. What you do get are big fights, and some of those fights should be swung by our heroes the PCs.
Let the PCs be the tide turner and decider of major battles, and play it up. Have troops be bolstered in morale because the PCs are around. Have NPCs break and run if a PC goes down, only to rally when they get back up and strike down their foes. Let them hear the cheers, the weight of the expectation, and like they're larger than life. Make them earn it, but let them feel it.
Protect Your Enemies
War is an easy place to lose any villains you hope to have be recurring, but it also gives you a lot of room to fudge things in your favor. PC take a lucky shot at an NPC? Have a bodyguard save them. Just don't do it too often or it becomes obvious. Still, war is not the time to put enemies on the field against PCs unless you're willing for them to go down, so take care with that too.
Have Fun, Make it Epic
In the end, I often found that mechanics can get in the way of the fun in war. This doesn't mean you don't need them, but don't be enslaved by them. Keep the flow going, keep the action thrumming, and keep the game moving forward as much as you can. War is a time of franticness and energy (battle anyhow). It shouldn't feel like people can wait an hour between turns just because. So don't let that situation happen.