Posted by: Vancian Notions | January 10, 2010

a 3.5 mass combat system

We interupt your regularly scheduled in character content for a draft 3.5 mass combat system
The system is built on a few assumptions. It is designed for moderately large scale (between 50 and  500 a side, at a guess) mass combat which allows PCs and other ‘specials’ to seemless be involved, and have a minimum of dicerolling.

There are a few basic concepts for this system:

1) Units.

A unit is a group of 5 or more homogenous troops. Troops will generally be a number of groups of 20 and/or one group of less than 20. Units of 5 or less will generally be assumed to retreat or be treated as individuals. Wherever

2) Dice rolls

Whenever you roll a d20 for a unit for attacks or saves, the following applies, depending on unit size. Whenever you roll, roll a d20. Apply the following rules based on that roll.

20; Assume the unit has rolled each number from 1-20 once.


  • if you rolled 11-20, count down from 20 until you run out of men.
  • conversely, if you roll 1-10, count up from 1.

10 or less

  • if the dice is odd, you have rolled the odd numbers (1,3,5,7…19)
  • If the dice is even, you have rolled the even numbers (2,4,6…20)

No matter how many are in the unit,

  • if you roll a 20,  one soldier who would otherwise miss hits for double damage
  • If you roll a 1, a soldier who would otherwise hit misses.


A unit of 17 city guard is attacking a group of orcs. The city guard hit on a 12 or more. They roll high, so are treated as hiving rolled 3-20. 9 of them hit.

A few turns later, having taken a lot of casualties,  they get fireballed. They need to roll 15 to save.  They roll 7, which is ODD and LOW. So they have rolled 1,3,5,7,9,11,13,15,17 for their saves – 2 saves, and the rest are in a world of hurt.

3) Damage

Once you’ve worked out how many of the troop have hit, each one does average damage, and any fractions are discarded. It’s important to note that ‘average damage’ vs creatures with DR is slightly more complex to work out, and will be filled in later. (we have a chart, basically).


when the city guard hit those orcs for the first time, they were using longswords and had strength 12, so were doing 1d8+1 damage, which has an average of 5.5. So those 9 hits do 49 damage to the orcs.

If the orcs had DR 5, then you’d need to work out the DR average damage – on a damage roll of 9,8,7,6 you do damage, so the formula is (4+3+2+1)/8, which is an average of  1.25 per hit, so the 9 hits would do 11 damage.

4) Initiative

roll initiative for each group of 20 as normal. See also combining units, below

5) Lethal and wound damage

In a normal fight with large volumes of dudes, you would tend to have, each turn, a number of guys killed and a number injured.

To simulate this, half (round down) of the damage dealt is turn is ‘lethal’ and half (round up) is ‘wound damage’

Lethal damage is applied first to the most wounded people in the opposing group and can kill them. Wound damage is applied to the most unwounded and if any are under half will be applied to those first, and otherwise spread evenly. Wound damage can only take people over 50% if there is noone under 50%.


The city guard deal 49 damage to the orcs. 24 points is ‘lethal’ and 25 is ‘wound’. The orcs have 15 HP.

The first 15 lethal damage kills an orc. The next 9 is dealt to another orc.

7 is the most wound damage an uninjured orc can be dealt, so 3 orcs take 7 and 1 takes 4

Note that you don’t work out how much damage each hit deals; just deal the damage and spread it as per the above.

A second unit of city guard hacks into the same unfortunate orcs, dealing them 55 (27 and 28). The 27 broken up as follows:

  • 6 to the orc on 9
  • 8 each to two orcs on 7
  • the remaining 5 to an orc on seven, putting it on 12.

4 orcs are also dealt 7 each.

6) Combining units

At the end of each turn, if their are groups of mutually homogenous units next to each other, one or more of which has taken casualties, reorganise them so that all but 1 of them has 20 soldiers in it. Take the soldiers from the higher initiative units and give them to the lower initiative units.

7) Unit formation

Units can be in one of three basic formations

a) Very tight (swiss guard, roman legionaries etc)

2 men per hex.In general, only highly trained units can be in very tight formation (Must have shieldmate, formation training or similar feats)

Formation has the following advantages and drawbacks.

  • +2 to attack and armour class (over and above any benefits from feats)
  • Cannot be flanked
  • +2 AC vs arrows
  • AOE spells are highly effective vs very tight formation. -2 to saves vs area spells and cannot evade
  • Further advantages may be possible (For EG pikemen etc) at GM option
  • All damage dealt is ‘lethal’ (The damage tends not to get spread around)
  • +4 to moral (note: Moral rules not written yet)

grouped formation

Grouped formation is 1 individual per hex. Most sorts of troops can adopt the grouped formation.

  • +1 to attack and defense
  • AOE spells can be dodged normally
  • Can only be flanked if at least three hostile groups are adjacent

Loose formation

Most untrained troops will mostly be in loose formation. In loose formation, troops have 5-10 feet between individuals.

  • Cannot use feats like shieldmate
  • can be flanked by any two non-adjacent hostiles
  • generally gets hit by less AOE attacks.
  • Where two units in loose formation engage, they are effectively intermingled. Intermingled units are hit by the same AOE attacks. Intermingled units all get +1 flanking bonus against each other and can sneak etc. If firing against intermingled units with ranged units, get a -6 penalty (instead of the usual -4) for being in melee. if you have precise shot, it is -2 instead (meaning you will ALWAYS deal damage to the friendlies!)

8) ‘Specials’

Dragons, PCs and other individual units are ‘specials’. Specials interact with units in exactly the same way as they would normally. They roll to hit and damage as normal, and cannot spread damage around. Troops will generally prefer other large units as targets unless the specials are obviously special (dragons etc) or they are ordered to do so by a leader. Individual specials in a group with a unit of non-specials generally cannot be targeted (except by MMs).

9) Leadership

Leadership is a skill which allows a character to direct troops, improve their moralle and improve their actions. Leadership is a class skill for bards, paladins, fighters, people with the leadership feat and some prestige classes.

A character with the leadership feat and no ranks in this skill has a default skill of charisma + non-level leadership bonuses (special reputation etc). example uses of leadership skill. If a character has the leadership skill+feat, they add the non-level leadership bonii to their skill. Leadership and diplomacy are mutually syergistic.

Rally troops: DC 20

Command troops: Dc15

‘Aid another’ troops: Dc15 (either attack or defence).

I think this covers everything?


All morale checks are will saves with modifiers based on how much damage the unit has taken, how many enemy have been killed, how powerful their foes are and if there are nearby specials directing the unit. Most Morale saves are DC 5 + the number of soldiers in the unit who have died. Standard morale modifiers are

  • Less than half original troop* still standing -4
  • Unit and allies have killed more than half of the total enemy force and more than half your side still alive +4
  • Cleric/wizard support /attack +2/-2
  • Your leader (via leadership feat) within command distance + non-level leadership
  • Your boss (either they pay you or you are a follower and they are an ally of your leader) – + NLL -5 (min 0)
  • No retreat possible +2

Edits: Added criticals. Added draft morale.


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