5e Mass Combat

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Brock Savage

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I am planning an adventure where my players are reclaiming a town from the clutches of Deep Ones. This is heavily inspired by the Raid on Innsmouth scenario from Chaosium's excellent Escape from Innsmouth supplement. I could use some help with a good system for running 5e combats involving at most 600 people on a side and more likely about a quarter that. I looked at the UA mass combat rules and am wondering if the system is satisfactory for combatants ranging from CR 1/8-CR 3, with the majority at CR 1/8. I feel like CR 1/8 fighters are just about useless even though that would make the bulk of most ancient armies.

Long story short, I am wondering if there is a suitable system for resolving this kind of combat.
 
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Strongholds and Followers has a decent mass combat system.
 
I remember the UA rules being slapdash, like it was missing key ideas - can't remember specific issues I read them once years ago. I'd rather wing it or do it statistically than use those.
 
I've always liked this quote.

“Out of every one hundred men, ten shouldn't even be there, eighty are just targets, nine are the real fighters, and we are lucky to have them, for they make the battle. Ah, but the one, one is a warrior, and he will bring the others back.”

― Heraclitus
 
My recommendation for any D&D Edition is to use AD&D 1st edition Battlesystem with the following modification for ascending AC.

Normally it works like this; 2d6+ THACO-AC + modifiers.

I played around with the numbers and found this works
2d6+Ascending AC-To Hit Bonus+modifiers.

One reason 1st edition Battlesystem works because the central mechanic is a chart that emulates X guys attacking at Y odds. The math behind the chart uses something called a binomial distribution. However Niles and Warner designed an excellent chart reduces everything into a roll and a lookcup.

Damage is dealt in hit dice not hit points. If you look at a 5e Ghoul you roll 5d8 for its hit point thus it has 5 HD for the purpose of Battlesystem. Since Ghouls are human sized they are represented by miniatures/units of 10 ghouls each and take 50 HD to destroy.

Nearly every spell and effect in various editions of D&D translate over on a one for one basis. Something that other D&D mass combat system don't do well including 2nd edition Battlesystem.
 
I've just finished up an AD&D Birthright campaign, and while we didn't use the mass combat systems (S&F, Battlesystem and the likes are too crunchy for our tastes) we did use the heck out of the Birthright Skirmish rules. We found it simulated mass combat well enough for our purposes, using HD instead of hit points and opposed d10 rolls with various minor modifiers. There's a write-up and rules summary on a blog somewhere out there, which I will try and find for you.
 
I appreciate everyone's input; these are good suggestions which have saved me a lot of time.
 
My first question would be what are the acceptable outcomes?

Can the the heroes side be wiped out? Defeated? Etc
 
My first question would be what are the acceptable outcomes?

Can the the heroes side be wiped out? Defeated? Etc
Good question. The PC side can absolutely be wiped out. A worst case scenario is the player army broken with the PCs finding themselves reduced to a fraction of their HP and in the middle of a rout.
 
Good question. The PC side can absolutely be wiped out. A worst case scenario is the player army broken with the PCs finding themselves reduced to a fraction of their HP and in the middle of a rout.
So from there I would assign what you think the odds of the various outcomes are and build or look for a system that matches that.
How (random, open-end) vs (semi fixed plotline) a game is it working in?
 
I've never found a mass combat (including skirmish) system for D+D that I actually like better than 3E Chainmail. This isn't just a nostalgic affectation - I keep 2 copies on my 'high use' shelf in the gaming book case and continue to use it at the table pretty often. It is just so solid as a self contained game system, and so perfect for resolving fights in a reasonable period of time.
 
I preferred the more streamlined Battlesystem that Douglas Niles created for 2e. Warmachine in RC is also solid.
 
I have a couple of requirements for a good skirmish/mass-combat system: 1) concrete movement and maneuver, using miniatures. Basically, mass combat is only interesting to play out if you allow there to be tactical decisions and consequences, which means keeping close track of where everyone is each turn. And 2) rapid, abstract combat resolution without book-keeping.
 
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