Welcome to Guidance, Private Sanctuary’s source for tips and techniques for the Pathfinder Roleplaying Game, written by Everyman Gamer Alexander Augunas. Today, we’re going to be talking about the ACR balance of mass combat.

Welcome back to Guidance’s coverage on the mass combat rules! If you need a refresher, here’s a link!

So last week we looked at the bare-bones of how mass combat works. This week we’re going to look at the mathematics behind it to ultimately determine what a “fair” encounter is. If you recall, in a previous article I stated that a “fair” encounter is where both sides have the means to reduce each other’s resources to 0. For normal combats, the CR threshold is APL +4. Ultimate Combat claims that an ACR 9 army versus another ACR 9 army is a relatively even fight, but as we’ve already determined, in standard combat a combat with the same CR as the group’s APL is skewed towards the PCs. Does that hold true in mass combat? Let’s find out!

Math Attack

The magic number here is ACR, which really determines everything about your army. An army’s Offense Modifier (OM) is equal to its ACR while its Defense Value (DV) is equal to its ACR + 10. Additionally, an army can modify its DV and OM by using the strategy track. So, assuming a Medium army with no strategy track, all armies tend to have a progression that looks like this.

This table is designed to show an army’s effective ACR based upon its size and the creature’s individual CR. The highest unmodified OM and DV you can receive with this system is +38 and 48 respectively. Considering that the formula for calculating ACR doesn’t change at all between army sizes or unit CR, this aspect of mass combat is relatively well-balanced, though it is interesting to note that if you assume both armies roll average (a d10), neither army will actually ever damage its enemy because hit point damage done by an army is determined by the amount that the army’s OM exceeds its opponent’s DV by. This is actually what makes the strategy track (and settlement modifiers to DV) so important to mass combat — these tactics and circumstances are the only real way that an army can either boost its OM (and lower its DV) to the point where damage can actually happen. This is also why the DV strategy track bonuses scale more slowly than the OM bonuses; OM always has a slight edge if everything else is equal, but grabbing that offense also makes it easier for the defending army to retaliate.

To this end, the only “real” variable in army combat is hit points, which can vary heavily based upon the type of unit that comprises the army. At low ACR, the difference is nearly negligible, but at high levels you’re looking at a difference of up to 90 hit points between wizard armies and barbarian armies, which makes sense.

Answering the Question

The entire reason I wrote this article was to answer a reader question that I received: does (my) CR + 4 strategy hold up for challenging PC armies? Well, let’s take a look at some sample stats. To make this work, we’ll assume that both armies are Medium and comprised of fighters for the purpose of determining their hit points.

• ACR 4 Army (22 hp; OM +4, DV 14)
• ACR 8 Army (44 hp; OM +8, DV 18)

Looking at these statistics, without relying on the strategy track, the ACR 4 army needs to roll a 15 or better in order to damage the ACR 8 army (roughly a 30% chance). If the army hits, the minimum amount of damage that it can deal is 1 (rolled on a 15) while the maximum is 6 (rolled on a 20). On average, the army has a 30% chance to deal 3 points of damage.

The ACR 8 army, on the other hand, only needs to roll a 7 or higher to hit (a 70% chance). The minimum amount of damage that it can deal is 1 (rolled on a 7) while the maximum amount of damage that it can deal is 14 (rolled on a 20). This army’s average damage is a 70% chance to deal 7 damage.

Assuming that everything is average, the ACR 8 army will win, without a doubt. Luck would have to be heavily skewed in order for the ACR 4 army to survive. In short, I think that if you plan on using mass combat, a “balanced” fight is two armies of the same ACR duking it out, while increasing an army’s ACR quickly sings the fight into the higher ACR army’s favor rather quickly.

Why is ACR Different?

You might be asking yourself, “Why is CR skewed but ACR not so?” The reason is simple: the Action Economy. In the example above, the ACR 4 army and the ACR 8 army have the same action economy: one attack per army turn. If you wanted to better mirror the advantage that PCs have in smaller confrontations, the best way to do this would be to allow each PC to control his or her own army and have the four go into battle together. Although there is still a good chance that at least one of the PC’s armies would be wiped out (especially if the ACR 8 army concentrated its efforts), the fight for the low-level guys would be slightly in the PC’s favor by about 1 CR. This is likely how humans and other creatures that typically don’t get to very high ACRs fight creatures with larger ACRs — they swarm. But in combats with one-on-one army confrontations, the money is always on the army with the better ACR.

I hope this answers your question, dear reader! Of course, I’ve barely scratched the surface of mass combat despite answering your question: after all, I didn’t talk about class special abilities or item enhancements or Kingdom Consumption! If you want to hear more about mass combat, or you have questions about the topic, leave me a comment below. Until then, your Everyman Gamer Alex Augunas is going leave until next time!

Alexander “Alex” Augunas has been playing roleplaying games since 2007, which isn’t nearly as long as 90% of his colleagues. Alexander is an active freelancer for the Pathfinder Roleplaying Game and is best known as the author of the Pact Magic Unbound series by Radiance House. Alex is the owner of Everyman Gaming, LLC and is often stylized as the Everyman Gamer in honor of Guidance’s original home. Alex’s favorite color is blue, his favorite Pathfinder Race/Class combination is kitsune commander, though an army of kitsune might be somewhat silly.