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D&D 5E Question on Mass Combat Comparison


The 2017 UA for mass combat had you assigning a battle rating to units based on CR and number of creatures. Then during a battle, both units would roll 1d20 plus their BR, and the winner accrued casualties on the loser. Great for in your head calculations and broad narrative, but then it falls apart.

For a broad guideline of relatively comparable troops the idea seemed okay. But if a unit with a battle rating of 40 (spearman say) fought a unit with a battle rating of say, 100 (heavy infantry), then the spearman would always lose and the infantry would never take any casualties. Ex, best roll for spearman is a 20, plus their BR of 40, equals 60. This would never beat the lowest roll of the infantry. (d20 =1, plus 100 for 101.)

Since 5e has an ethos of bounded accuracy, I would think the lesser unit would do some damage, and eventually enough of those units would attrit the infantry.

So I toss that idea out. But I want a system that I can look at a stat block and use a number from it and come up with a broad narrative idea of who wins, but could be surprised by a turn in the battle of lucky rolls.

Primeval Thule has a similar system that adds up the the CR of the creatures involved, then rolls dice, but even if the winner wins the oppossed roll, they take some damage, leading to eventual attrition.

To determine the combat power of a side add up the total Challenge Rating of the combatants. Count anything less than ½ as ½ and round fractions down. Do not include the PCs. Challenge Rating is a good measure of an individual creature’s ability to both absorb damage and dish it out, so the total CR of a formation is a reasonable estimate of its strength. For example, if a PC is leading a raid of 75 tribal warriors (CR 1/8) with a tame tyrannosaurus, the war party has a combat power of 37 for the warriors and 8 for the tyrannosaurus, for a total of 45. The base damage inflicted by a warband each round is equal to 20 percent of its current combat power, rounding down to the nearest whole number (minimum 1). In the example above, the base damage for a war party of 75 tribal warriors and their T Rex is 9 (45 times 20 percent).

At the end of each round of combat, after you have resolved the actions of the PCs and any monsters or villains they’re handling in person, resolve one round of follower combat. The attacking and defending forces make an opposed battle roll (d20); the side with the higher result “wins” that round, and deals their base damage to the combat power of the losing side. The losing side deals ½ of its base damage to the winning side. If the result is a tie, neither side takes any damage—the fighting was inconclusive.

I like simple systems like this that I can do in my head, and statistically predict probable outcomes. Then let the players actions swing things around. So I'm not looking for replacement systems, or systems with unit cards or token, or minis etc.

Just an idea if there are any flaws with Thule's system like there are in WotC system that I may have missed, or ways to improve the fidelity of either system.


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The ties in Thule's system seem odd. Everyone is always taking damage every round, unless there's a tie and all of a sudden no one is taking any damage? I would have a tie do half damage to each side. And even though it is counter intuitive, I would have each side do their own damage to themselves on a tie. That way a tie is still better for the weaker unit and worse for the stronger unit than the average result.


If you aren’t interested in switching systems, I don’t have much to offer. I can say that I was wholly unimpressed with WOTC’s attempt (and judging by the fact that it never made it to print, I imagine they weren’t happy either).

I created my own homebrew system that mixes player interaction and reliable (or at least, somewhat predictable) math.

The basic premise is that it’s tic-tac-toe (yes, I’m serious). Each “zone” is an encounter, and each encounter is made up of enemies (set to a Hard CR encounter), terrain, and specific win/loss conditions.

The Battle Round consists of:
  1. Player Phase. The players can choose what zone(s) they want to directly intervene in (they can split up, but the Encounter Difficulty doesn’t change). You throw down a map and have a battle. If they win, draw a circle. If they lose, draw an X.
  2. Battle Rolls. Once the PCs have resolved their encounters, each zone will resolve with a single 2d6 roll (the players roll):
    1. 1-3: Critical Failure (the zone is won by the enemy)
    2. 4-6: Failure (the zone is crumbling, and the next Battle Roll for this zone will be made at a -1; this modifier stacks)
    3. 7-9: Success (the zone is advancing, and the next Battle Roll for this zone will be made at a +1; this modifier stacks).
    4. 10+: Critical Success (the zone has been won by allied forces).

Get three in a row (like tic-tac-toe) and the players win a heroic victory. If you can’t get three in a row, you count the number of zones each side has won - the side with the most “wins” the battle, but takes heavy losses.

It sounds dumb, but having done it four times, it’s been a smash hit every time. The players get to participate, the dice make things exciting (but the 2d6 roll is easier to rely upon compared to 1d20), and the resource loss automatically creates tension.

There’s more advanced stuff you can do - like Assets for each side (an elite cavalry unit that the players recruited grants them a +1 on a Zone, for example). I know it’s not exactly what you were asking for, but it’s worked great for me!
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@grimmgoose I like your idea and might give it a closer look at some point.

Does the type of unit in any given encounter square have any bearing on the success change or 2d6 roll?


Does the type of unit in any given encounter square have any bearing on the success change or 2d6 roll?

No, but that doesn't mean you couldn't add that.

I originally meant to keep it pretty abstracted - the Assets that the players pick up are simply "wins" they've gathered over the course of the campaign. So, for my upcoming Mass Battle, I'm tracking the following Allied Assets:
  • Tor Sethai Dwarf Breakers. If the players successfully train the elven recruits at Tor Sethai, they gain this Asset, which grants a +1 to the Zone they are deployed on.
  • Deathstalker Assassins. If the players find and destroy the Scarlet Crusade expedition (yes, I directly stole it from WoW - I'm not ashamed), they gain this Asset, which lets them deploy 2x Deathstalker Assassins as allied units for one encounter.
As we keep playing up to the Mass Battle, and depending on their actions, I might add more.

The Enemy Assets I'm preparing are:
  • Frostweave Shardstorm. This powerful floating shard disrupts allied movement in this Zone, giving a -2 penalty to the Battle Roll. If engaged as an Encounter, it becomes a Lair Action, acting in Initiative Count 20, dealing 2d10 Necrotic Damage in a 15-foot radius sphere centered on a point. This Asset moves randomly (roll 1d10, ignore a result of 10).
  • Hellspore. This goremound has created a rancid, thick-green smoke obscuring demonic activity. All adjacent Zones suffer a -1 to the Battle Roll. This Asset cannot move.
  • Faithbreakers. This elite unit of demons increases the combat difficulty of a Zone, granting enemy reinforcements of 3x bearded devils and 1x maw demon. This Asset cannot be destroyed through a Battle Roll; it must be destroyed via an encounter.

Typically, if an Asset is in a Zone that is lost, the Asset is destroyed, but in the case of the Faithbreakers, I wanted to add the temptation of the players directly choosing to confront them in an encounter.

edit: to clarify, the +1, or the -2, etc. are modifiers to the Battle Roll. So normally, the Battle roll is 2d6 +/- crumbling/advancing +/- Asset Modifiers.

For example, if the players deploy the Dwarf Breakers on a zone at the start of the battle, that Zone's Battle Roll is 2d6+1.

I actually prefer the general ideas behind Exalted's mass combat: the leader of the unit is the baseline, the unit then essentially modifies them and allows them to participate at scale. So a unit led by a fighter would have the fighter's attack bonus +/- a mod based on how well equipped the unit is, and dmage that starts witht he fighter's damage +f(x) based on the size of the unit. It should look like Dynasty Warriors (one big hero mowing down crowds of mooks, while followed by their own crowd of mooks) rather than anything realistic.

Why is this good? Because it keeps the story about the main characters, and lets the players use their pc's rather than brand-new statblocks that work differently. It makes mass combat an extension of the game, rather than a whole new game tangential to the regular mechanics.

Downsides: obviously "realism" is not a priority here, so this will simply not work for some people. Also it doesn't really account for two pcs in the same unit, though I'd just not do that rather than try to figure out how to make it work.

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