5e DMG: page 250 as a complete mass combat system

The 5e DMG has a short section on “handling mobs:” it has a chart for approximating, out of a group of attacking monsters, how many monsters hit.

It’s pretty simple: subtract attacker’s hit bonus from the target’s AC. Cross-index that number on the chart. If the number is 1-5, all the attackers hit; if it’s 6-12, 1/2 of them hit; etc., up to 1 in 20 of the attackers hitting on a 20.

I ran a big set-piece battle yesterday: 8 mid-level PCs and 10 gnomes against 20+ drow and other assorted creatures, including a drow spider chariot and a sinister angel. With a wizard and a sorcerer PC and two drow wizards, all slinging fireballs, the mob attacks weren’t much of a factor. With all those fireballs, what I COULD have used was rules for mob saving throws.

If I’d thought about it, I’d have realized that the same chart can be used for saving throws. Instead of subtracting attack bonus from AC, subtract saving throw bonus from DC, and use the chart as normal. For instance, a fireball save DC of 15, minus the drow dex save (+2) is 13, which, according to the chart, means that 1/3 of the drow succeed on their saving throw (and probably survive with 1 or 2 HP left).

In fact, this same chart can be used for ability/skill checks (how many orcs managed to climb the wall? DC minus skill bonus) or any other d20 roll.

To me, it seems this is all you need to run fairly simple battles with dozens or hundreds of creatures per side. The amount of HP tracking is not excessive: for instance, in this unit of 50 ogres, 24 have 15 damage and the other 25 have 30 damage. (For ease of bookkeeping, assume that melee attacks always target the most-damaged creature.)

You might also care about the base size of big units. I assumed that a close-packed formation of 10 Medium troops took up the size of one Large creature. I’d say that 25 troops are Huge and 50 are Gargantuan.

If we do any bigger-scale battles, I might find other rules that I need (after all, the Chain Mail rules are much longer than this blog post) but right now, this is looking pretty good for running big D&D skirmishes.

7 Responses to “5e DMG: page 250 as a complete mass combat system”

  1. trespassers says:


  2. Matt G says:

    yeah! I should have read that page more carefully. I could have used it when deciding lizard folk vs. bullywugs in my recent Hoard of Tiamat game. I will definitely remember it when we get to the big finale fight. I can let the Players do most of the rolling so they feel more invested in the outcome.

  3. 1d30 says:

    I just use the normal combat rules but group monsters into units of 6. A unit rolls to hit against another unit: it hits or misses as a whole. Say you have a unit of 5 orcs hitting a unit of 6 farmers: roll d6 orc damage, x5 for 5 attackers. The unit of farmers absorbs damage until a farmer hits 0, which becomes a casualty, and we have 1 fewer farmer in the unit.

    The whole unit, no matter how many there are, fits in a 10′ square (assume they work together really well, or just assume 3 across and 2 ranks like certain editions of D&D). The unit is a d6 on the table; each pip is a creature.

    (I tend to ignore excess damage unless it’s close to taking out another fighter by the end of the round. That way I don’t keep track of individual HP. I might retain a sense that this unit is “fresh” meaning it has no injured guys, or that unit is “bloody” because it took a little extra damage last round but not enough to lose a man.)

    Allied units tend to even out when they meet up. So a d6 showing 4 orcs meeting ad6 showing 1 orc, I’ll have the 1 orc join the 4 leaving only one die with 5 pips. This reduces the number of moving pieces without reducing combat effectiveness.

    At this scale, PCs can still operate individually. If two or more want to stick together, I tell them to pick a “leader” figure which represents all members of their PC unit. The other minis get grouped to the side together.

    The scale also works for outdoor fights, although if you triple scale outdoors for 1E/2E rules you end up with creatures not exactly filling up the space. In this case I can stack dice, which has the added bonus of not revealing exactly how many are in the lower units, and I bunch up the dice instead of putting them in their own little squares. Still use the squares or hexes for calculating movement and missile range though. Calculating spell area effects is just as easy as in the normal game.

    I picked up a little baggie of 100 tiny 6mm mini d6 of various colors. I’ve used those for small creatures (rats, kobolds, bats) in 1″=5′ scale, with HP equaling die pips. I also used them for units of creatures in mass combat with scale 1″=30′. Because they’re different colors, I was able to call the green ones Orcs, the red ones Mercenaries, the white ones Skeletons, etc. I believe slightly larger dice would work better so people can see them easier – probably a 12mm die would be perfect so it fits 4 per inch (2×2).

    I would love to get people to use 12mm minis. I’m sure you could paint them to be distinctive enough. But I think especially for imperfect lightning, failing vision from reading too many books, and distance from player to map because of imperfect table size, the 25mm minis are still a good compromise.

  4. paul paul says:

    Funny, 1d30, that’s pretty much what I did throughout 4e, having everyone in a unit use the same attack/damage roll: and I also use mini d6es to track how many people are left in a unit. Great minds etc.

  5. paul says:

    Lol. Four days later, WOTC releases their official mass combat system. http://dnd.wizards.com/articles/features/unearthed-arcana-when-armies-clash

  6. VG says:

    This is amazing, thank you!

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