Simple-ish Mass Combat/Battle Rules

Hopefully these rules are simple enough once the base concept is understood. They are also intended to be fairly deadly, and so hopefully these rules will resolve battles relatively quickly.

Mass combat

Overview
Units are treated as single combatants, they have Unit Health (UH), Unit Attacks (UA) and Unit Damage (UD) per hit done. The units are largely a macro-version of the monster/troop within the unit.  The following is explained with reference to the following three reference units:

Reference units:

Unit 1    105 Human spearmen (HD1, AC7, NOA 1, DA1-6)
i.e. unit stats –> 105 UH; 11 UA; 10 UD

Unit 2    20 centaurs (HD4, AC5, NOA 2, DA1-6;1-6)
i.e. unit stats –> 80 UH; 16 UA; 10 UD

Unit 3    1 T-Rex (HD18, AC7, NOA 3, DA1-6;1-6;5-40)
i.e. unit stats –> 18 UH; 6 UA; 20 UD

Quick summary of unit stats

UH = Total HD of unit
UA = UH/10 (rounded to nearest whole number) x NOA
UD = usually 10 UH damage is done per hit (but powerful monsters could do 20 or 30 UH per hit)

So, UH equates to the ‘hit points’ of the unit, UA equates to the number of attacks of the unit and UD equates to the damage per hit made by the unit. UD is the only thing worth pre-determining, as everything else is done on the fly.

Unit stats

:: Unit Health (UH) of the unit is equal to the total HD of the unit, i.e.:

Unit 1 – 105 UH (i.e. 105 x 1HD)
Unit 2 – 80 UH (i.e. 20 x 4HD)
Unit 3 – 18 UH (i.e. 1 x 18HD)

:: Unit Attacks (UA) of the unit is equal to UH divided by 10, and rounded to the nearest whole number and then multiplied by the troop type’s Number of Attacks (NOA):

Unit 1 – 11 UA (i.e. 105 UH ÷ 10 x 1NOA and rounded up)
Unit 2 – 16 UA (i.e. 80 UH ÷ 10 x 2NOA) i.e. centaurs get two attacks per round.
Unit 3 – 6 UA (i.e. 18 UH ÷ 10, rounded up to 2, and x 3NOA)

:: Unit Damage (UD) per successful attack made is determined on a power scale, i.e.:

10 UD    (where the maximum damage possible divided by NOA is in the range 1-10) – i.e. normally the case

20 UD    (where the maximum damage possible divided by NOA is in the range 11-20) – i.e. for powerful monsters that can do damage in the range 11 to 20 hps

30 UD    (where the maximum damage possible divided by NOA is in the range 21-30) – i.e. for very powerful monsters
etc.

So:

Unit 1 – 10 UH (max damage i.e. 6 ÷ 1NOA = 6) –> ‘normal’ damage category
Unit 2 – 10 UH (max damage i.e. 12 ÷ 2NOA = 6) –> ‘normal’ damage category
Unit 3 – 20 UH (max damage i.e. 6+6+40 ÷ 3 gives 17) –> second damage category

Combat Method

:: Treat combat as one unit fighting another, e.g. treat a unit of 105 humans fighting a unit of 20 centaurs as Unit 1 fighting Unit 2.

:: Wipeout rule – if a unit loses initiative and is whiped out in the first round, the wiped out unit still does half damage on their adversary

:: Defeat Morale – check unit morale if the unit suffers more UH damage than the other side

:: Decimation Morale – check unit morale if the unit lost more than 50% of their UH in one round

:: Defeat and Decimation Morale tests are independent of each other

 

 Examples using AD&D combat tables to resolve combat (to hit rolls not shown)

 Example 1:
Unit 1 attacks Unit 2 (in this scenario Unit 1 is lucky and wins initiative each round):

Round 1:
Unit 1 has 11 Unit Attacks
only 3 attacks hit; and so do 30 Unit Health damage
–> Unit 2 is reduced to 50 UH (i.e. 80-30=50 UH)

Round 1 cont…
50 UH of the remaining centaurs in Unit 2 fight back; they have 10 Unit Attacks (i.e. 5 x 2NOA)
6 hits are made; and so do 60 Unit Health damage
–> Unit 1 is reduced to 45 UH (i.e. 105-60=45 UH)

The humans lost the combat round taking the most UH damage, and lost more than 50% of their UH in a single round, and so need to take a Defeat Morale check and a Decimation Moral check. They pass, but is luck truly with them?

Round 2:
Unit 1 with 45 UHs gets 5 Unit Attacks
2 hit; doing 20 Unit Health damage
–> Unit 2 is reduced to 30 UH (i.e. 50-20=30 UH)

Round 2 cont…
Unit 2 with 30 UH fights back, they have 6 unit attacks (i.e. 3 x 2NOA)
3 hit; doing 30 Unit Health damage
–> Unit 1 is reduced to 15 UH (i.e. 45-30=15 UH)

This time Unit 1 does not make both morale checks, and they flee for their lives.

Example 2:
Unit 1 attacks Unit 3 (in this scenario Unit 1 wins initiative):

Round 1:
105 humans have 11 Unit Attacks
only 3 hit; doing 30 Unit Health damage
–> Unit 3 is reduced to -12 UH (i.e. 18-30= -12 UH)

Round 1 cont…
Because the T-Rex lost initiative and is destroyed in one round, it still does half damage:
18 UH of T-Rex gets 6 Unit Attacks (i.e. 2 x 3NOA)
6 hits are made; doing 120 Unit Health damage (i.e. 6 x 20 UD)
but this is halved to 60 UH damage due to the initiative rule mentioned above
–> Unit 1 is reduced to 45 UH (i.e. 105-60=45 UH)

While the human spearmen bravely seized initiative and destroyed the T-Rex, it was at a high cost. Indeed, despite winning the clash, they failed their Decimation Morale check (i.e. they lost more than 50% of the unit in one round) and so left the field believing they had done more than their fair share of the slaying in this battle.

Example 3:
Unit 1 attacks Unit 3 (but in this scenario Unit 3 wins initiative):

Round 1
18 UH of T-Rex gets 6 Unit Attacks (i.e. 2 x 3NOA)
6 hits are made; doing 120 Unit Health damage
–> Unit 1 is smashed by the T-Rex in a terrifying display of power

Round 1 cont…
Because the Humans lost initiative and were destroyed in one round, they get to do half damage in return:
105 humans have 11 Unit Attacks
only 3 hit; doing 30 Unit Health damage; but this is halved to 15 UH
–> Unit 3 is reduced to 3 UH (i.e. 18-15=3 UH)

In destroying the swarm of pesky humans, the T-Rex is very badly speared in hundreds of places. Even if it made its morale check, 3 UH does not qualify for a UA point (i.e. 3 divided by 10 (and rounded to the nearest whole number) x 3NOA is 0 UA). The hefty beast limps off the battle field, but not before chomping down on a few of the chewy humans.

Finally
I suspect that there are already some pretty good mass-combat rules out there. But, … I thought I’d have a go at my own (before getting cross-polinated by other people’s ideas) … you know, for the fun of it.

– – –

InHotS the cover imageMe on DriveThruDriveThru; at the moment I’m mainly pimping my procedural High Seas ‘Hex Crawl’ – In the Heart of the Sea, and my procedural Wilderness Hex Crawl – In the Heart of the Unknown.

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