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Monday, May 01, 2023

Old School Mass Combat I - The basics (attacking, taking damage, and saving throws)

The idea started here but you can definitely skip the other posts. This is a straightforward rewrite that will be easier to understand, while the other posts were mostly brainstorming. 

My goal is creating a mass combat system that fulfills the following criteria as much as possible:

- Perfectly compatible with B/X*. 
- Minimal conversion needed.
- Avoid approximations. AC 4 and AC 5 are different things, and having 5 HP is better than 4.
- Results that are similar to individual combat.
- No new units needed, use ANY humanoid or monster in the book.
- Avoiding new mechanics, such as using 1d6 or 2d6 for attack rolls.
- Miniatures and maps are optional, you can go full "theater of the mind" if desired.

(*This also means it could be used with other OSR and TSR games with minimal conversion, for example, adding +1 to you attack bonus, etc. You can use it for Dark Fantasy Basic as written, using ascending AC).

Notice that most existing systems do not fulfill these criteria, including chainmail and other cool systems that use 2d6 attacks, 1d6 attacks or different armor values, for example. In my system, AC, damage, etc., is kept exactly the same.

First, we are proposing two systems. You can use either or both, depending on the circumstances. The first system (detailed) uses units of 20 individuals as a starting point and has very precise results when compared to individual attacks. The second system (freeform) uses any number of individuals. It is easier to use but the results do not map perfectly to individual attacks.

These two systems are for calculating damage output. Every other rule (taking damage, morale, fighting individual PCs and NPCs, etc.) applies equally no matter which system you choose.

TBH, as a fan of minimalism, I'm very close to just abandoning the detailed system altogether. Skip to the second one if you want.


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1a) The detailed system

Start with a of 20 NPCs per unit. When a unit attacks a monster or other units, it doesn't make an attack roll. Instead, it simply roll for damage. The damage caused by a score every turn is equal to the damage caused by an individual multiplied by [21-THAC0+AC].

Unit damage = single damage * [21-THAC0+AC]

An unit of veterans, for example, causes 1d8 * [2+AC]. Against a target with AC 4, they cause 6d8 damage per round.

If you're using ascending AC and attack bonus (AB) instead of THAC0, the formula is NPC DMG*(21+AB-AC). The results are exactly the same (e.g., the veterans cause 6d8 damage, etc.).

If you want units of 100, 200 or 1000, just multiply the damage by 5, 10 or 50 as appropriate.

Smaller units should divide damage as appropriate (e.g., an unit of 10 NPCs deals half damage - 3d8 in our example). One possibility could be just attacking as normal until you're reduced to 10 NPCS, and only then reduce damage by half.

Units of 13 or 17 are possible but the math gets harder: roll damage, divide by 20 and multiply by 13 or 17. You can use approximations if you want (e.g., an unit of 6 or 7 just deal one third of the original damage), move on to the freeform system, or fall back to individual attacks when there are few NPCs left.

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1b) The freeform system

In the freeform system, the damage of an unit is equal to the sum of all individual damage, averaged and divided by three. For an unit of 20 veterans, it would be 30, for example (20d8, average 90, divided by 3).

To hit, simply make three separate attack rolls. Each successful attack inflicts 30 points of damage. 

Three is an arbitrary number, of course - you might as well divide the total damage by ten or twenty and roll as many dice, but three attack are enough for me.

If you lose about a third of your unit and don't want to recalculate, you could reduce to two attacks instead. However, recalculating is very easy even without a calculator (17 veterans cause 17d8 damage, a bit less than 6d8 when divided by three, so let's say about 25 damage per attack) - or, if you prefer, calculate (or even roll 6d8) after you hit.

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2) Taking damage

When an unit takes damage, just divide it evenly to see how many NPCs are down. A group of 20 veterans (4 HP per NPC) taking 30 damage loses 7 individuals, excess damage is discarded.

Notice these individuals aren't necessarily dead, but they are out of the combat for all intents and purposes.

Single figures (e.g., a single dragon in the battlefield) loses HP as normal. If they survive, they might test morale, and they start the next round with fewer HP.

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3) Saving Throws

Use the same reasoning, rolling once for every third of your unit. Area damage might be treated differently; see "area attacks", to be resolved in another post.

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And... that's it. It is enough to create all kinds of mass combat. The rest are special circumstances that have to be treated separately, including: 

* Initiative
* Movement and attacks (charge, melee, ranged)
* PCs and powerful monsters
* Leaders
* Mounts
* Spells and other area attacks (a fireballs affect about a  dozen NPCs in formation?)
* Flanking
* Maximum number of attackers
* Prices
* Time (turns etc.)
* Fortifications
* Melee weapon reach

Also, the fact that I'm not using HD instead of HP and d6s instead the d20 might deserves an addendum.

21 comments:

  1. This is great, I've started making an adaptation for my own games - https://simonyrpgs.blogspot.com/2023/05/diaz-freeform-mass-combat-system.html

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    1. I'll probably use units of 20 in my main 5e game to start with as I use the 1e DMG follower table and it tends to produce results like 20 cavalry + 100 infantry.

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    2. Neat! I will love to see how it goes and how it can be adapted to 5e!

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    3. Been doing some work on scaling. My thinking is that small battles stick with 1"=5' personal scale, while large battles can use a 1"=50' scale.

      Scaling
      This system is designed to work with the 1:1 rules, and so typically uses the same base scale of 5' = 1 square (1" on tabletop). For larger battles a scale of 1"=50' may be used. Units of 20'x20' or larger size use square bases.

      Unit Size (Range) Base Area
      10 (6-14) medium 15'x15' (9 squares)
      20 (15-24) medium 20'x20' (16 squares)
      30 (25-34) medium 25'x25' (25 squares)
      40 (35-44) medium 30'x30' (36 squares)
      50-60 (45-64) medium 35'x35' (49 squares)
      70-80 (65-84) medium 40'x40' (64 squares)
      90 (85-94) medium 45'x45' (81 squares)
      100 (95-104) medium 50'x50' (100 squares)
      On the tactical battlefield, units of more than 100 medium-size creatures should be divided up into multiple units, each of 100 or fewer individuals. Eg a Cohort of 400 men makes up 4 units each of 100 men. A Battalion of 800 men makes up 8 units each of 100 men.

      Unit Size (Range) Base Area
      10 (6-14) large 30'x30' (36 squares)
      20 (15-24) large 40'x40' (64 squares)
      30 (25-34) large 50'x50' (100 squares)
      On the tactical battlefield, units of more than 30 large-size creatures should be divided up into multiple units, each of 30 or fewer individuals. Eg a cavalry company of 120 cavalry makes up 4 squadrons each of 30 cavalry.

      Unit Size (Range) Base Area
      5 (3-7) huge 30'x30' (36 squares)
      10 (8-12) huge 50'x50' (100 squares)
      On the tactical battlefield, units of more than 10 huge-size creatures should be divided up into multiple units, each of 10 or fewer individuals. Eg a frost giant platoon of 40 giants makes up 4 squads, each of 10 giants.

      Unit Size (Range) Base Area
      5 (3-7) gargantuan 50'x50' (100 squares)
      On the tactical battlefield, units of more than 5 gargantuan creatures should be divided up into multiple units, each of 5 or fewer individuals.

      Movement Rate per Round at 1"=50' Scale
      20' (Dash 40'): 1" Double Move (no attack)
      30' (Dash 60'): 1" Double Move (no attack); with 30' bonus move action, may move 1" & attack
      40' (Dash 80'): 1" Move + Attack, 2" Double Move (no attack)
      50' (Dash 100'): 1" Move + Attack, 2" Double Move (no attack)
      60' (Dash 120'): 1" Move + Attack, 2" Double Move (no attack)

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    4. For tabletop, this also gives me an excuse to use my old Battlesystem cardboard counters. :)

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    5. Awesome stuff!

      I'm not sure, I am considering 1:10 scale.

      The thing I'm afraid of is initiative, as two similar units facing each other would finish the fight in a singe hit.

      Does Battlesystem use 5' squares? I thought it was 10' in the TSR era for some reason.

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    6. It doesn't use squares. The tokens fit in a 1" square - even the dragons.

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    7. Or maybe I'm thinking of TSR dungeons having 10' squares. It would be very useful to know the area an NPC occupies in TSR D&D (for area attacks etc.), will look into it.

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    8. I've been working on a 10:1 scale battle setup for my 5e game - 950 orcs & goblins vs the PC domain and its 320 soldiers & militia. >:)

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    9. "The thing I'm afraid of is initiative, as two similar units facing each other would finish the fight in a singe hit." One good thing about 5e's bloated hp totals is that this can very rarely happen with most troop types. Although I'm giving reach weapons like halberds & pikes +50% damage (rounded down), and goblins are notably squishy (7 hp); so a halberd unit doing 10 damage/man will go through 7 hp goblins like a hot knife through butter. More typically a typical troop type does 4-6 damage and has 11-16 hp, so 2-4 hits to kill.

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    10. Ah, yes, 5e is easier in this regard.

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    11. I've been lowering unit damage for larger scales using standard time (1 round = 6 seconds, in 5e), reflecting that not everyone can get into melee every round. From full damage at 10:1 scale to 30% at 100:1 scale.

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    12. I'm rethinking the whole thing, TBH... I really like your 10:1 scale. 100:1 starts becoming a bit abstract to me, not sure.

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    13. Yeah, I agree and when I hopefully run a mass battle soon it will be at 10:1 scale. With say 20 10-man squads in a battle line that's still a lot of d20s!

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  2. Re TSR scale, Gygax suggested 3 men side by side in a 10' corridor. So with modern minis, 1"=3.3 ft or 1 meter would work.

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    1. Thanks! Not sure this would work in an outdoors formation. Maybe use the modern 5' square, or any area attack will wipe entire units at once.

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    2. In 1e Battlesystem a fireball can affect 2 10-man units, each covering a 20' square. I'm currently going with a 10 man unit covering a 15' square.

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  3. Just thinking re one (eg PC) vs many combat. I see two alternatives. One: the PC fights only the front line of the unit. They get 3 individual attacks. Two: the PC is surrounded by the unit. They get 8 individual attacks (or 5, if bloodied, below half hp). This works great using a 3x3 unit base at 10:1 scale, a PC in the middle of the enemy unit has 8 adjacent enemy squares.

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    1. I think AD&D ahs an answer for single figures (8 individual attacks sounds about right). I like the idea of 3 attacks if the PC is in the frontline, will definitely try to incorporate that!

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    2. Yes the AD&D 1e DMG has diagrams for using squares & hexes.

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