Abstract Fast Combat System for GURPS

Abstract Fast Combat System for GURPS

As was outlined several posts ago, GURPS lacks an abstract fast combat system that can be used to resolve engagements, especially ones that have a scale between individual combat and mass combat. I thought about it, and I believe that the best option would be to combine parts of GURPS Mass Combat with the mass combat from ACKS II RR / Domains at War: Campaigns. For that, we will have to calculate the BR (Battle Rating) values for each combatant, which isn't actually that difficult.

The design goal of this system is to have a way to resolve combat quickly between almost any numbers of combatants. While I absolutely adore the nitty-gritty detailed combat system of GURPS, I realize the need for abstraction because resolving, for example, a random encounter between 5 PCs and 20 mercenaries on one side and 60 orcs on the other side is practically impossible on the standard GURPS scale. Let's see if I manage to write something that makes sense.

But wait a second? Do I really need to write anything? The purpose of BR is to avoid using Troop Strength from GURPS Mass Combat to be able to tie it better to the economical systems of ACKS, and be able to calculate BR instead of using Heroes on the Mass Scale. It seems that the entire GURPS Mass Combat procedure should work well if you just replace TS with BR, while keeping the element classes (Fire, Armor, etc.). However, some adjustment might be required, so let's run several hypothetical examples to see if it works.

BATTLE #1 - Regular Mass Combat

To refamiliarize ourselves with the rules, let's first run a "normal" battle scenario in GURPS Mass Combat. First, we will need two armies, but using ACKS Battle Ratings instead of GURPS Troop Strength. ACKS II lists individual BR in the troop summary tables (p. RR439-441) and unit BR in the unit summary tables (p. RR442-444). In addition to the more common troops described in RR, there are BR values in the Monstrous Manual. It should be noted that unit BR is rounded to the nearest 0.5. I've already more or less worked out the procedure of converting GURPS stats to ACKS BR, but I'll describe it later. For now, let's draft two armies using premade units. Since ACKS doesn't have element classes, I will assign them myself.

Army A

120 Light Infantry (BR 1)

120 Light Infantry (BR 1)

120 Heavy Infantry A (BR 2)

120 Bowmen (BR 1.5, Fire)

Total BR: 5.5

Total Fire BR: 1.5

Army B

120 Orc Light Infantry (BR 1)

60 Kobold Weasel Riders (BR 7, Cv)

120 Kobold Bowmen (BR 0.5, Fire)

Total BR: 8.5

Total Cv BR: 7

Total Fire BR: 0.5

As you can see, the armies are uneven, but this is intentional. How long will a battle round be? GURPS Mass Combat says that the round length depends on the number of elements in the smaller of the fighting forces. Each element is usually comprised of ~10 men or ~5 mounted soldiers. Thus, Army A effectively has 12 + 12 + 12 + 12 = 48 elements, while Army B effectively has 12 + 12 + 12 = 36 elements. Thus, according to table on page 32 of GURPS Mass Combat, a round will be 30 minutes long.

Note: This should be further extrapolated to account for battles with less than 1 element. I believe that 1-minute rounds should work well on that scale.

What's missing? Both sides should have commanders with the Strategy skill, and we also have to determine the terrain because it affects the chance of achieving a surprise attack.

Army A: Strategy-14

Army B: Strategy-11

Terrain: Hills (Terrain Rating 6)

I intentionally gave Army A a better commander to compensate for their relative weakness.

Note: Since GURPS Mass Combat by default assumes rather large engagements, it uses the Strategy skill. However, there is the Battling Monsters box on page 27 that says to assign a "Cunning" value to monsters or small, disorganized groups of monsters. Cunning should be the higher of IQ or Perception. However, when does Cunning become Tactics, and when does Tactics become Strategy? This is something that should be clearly defined in the future to make it all work.

The first step is the Reconnaissance Contest (p. 28-30) because initiative and surprise is important. This is a Quick Contest in which each force rolls against the average of its intelligence chief's Intelligence Analysis skill and its commander's Strategy skill, rounded down. Of course, there is a list of modifiers.

Note: Interestingly enough, there is no Battling Monsters equivalent for reconnaissance contests. Thus, by RAW, monsters are very easy to ambush. Perhaps, monsters should roll against their Vision, Perception, or Observation instead, and at a certain point Tactics should come into play too. This is another aspect that has to be defined clearly in the future.

For the sake of simplicity, let's assume that both armies have Intelligence Analysis at the same level as their Strategy. Both armies are on the move. Let's say that the beastman army is invading, so their relationship with the locals is hostile, so they get a -1, while the human army gets a +1. Both armies also take a -1 due to not having any Recon elements in a land battle. Thus, Army A rolls against 14 and gets 11 (MoS 3), and Army B rolls against 9 and gets 5 (MoS 4). Army B is the winner, but the margin of victory is lower than Terrain Rating. Thus, this is not a surprise, but initiative instead. This means that Army B has a choice between a prepared pitched battle or a hasty encounter battle. Let's have an encounter battle.

Before the battle happens, we have to calculate the Basic Strategy Modifier. First up is Relative Troop Strength (p. 31). We're using BR here, but the process is the same. We divide BR 8.5 by BR 5.5 and get 1.54. This odds factor (1.5:1 or more) gives Army B a +2 bonus to Strategy.

Then, we calculate Special Class Superiority (p. 31). Army B has cavalry (Cv), while Army A doesn't have any. This automatically counts as 5:1 odds factor that gives +3 to Strategy. Army A has Fire BR 1.5, while Army B has Fire BR 0.5. The odds factor is 3:1, which gives +2 to Strategy to Army A.

Thus, Army A has Strategy 16 (14 base + 2 Fire superiority), and Army B has Strategy 16 (11 base + 2 relative troop strength + 3 Cv superiority). See? The armies evened out, even though I didn't really intend it. But that's okay.

Since this is an encounter battle, we skip the Defense Bonus.

Now we fight! Each round (30 minutes in this case) involves several steps.

Round #1

1. Risk

Here, each commander and individual PC must choose a risk modifier between -3 and +3. (ACKS II has a similar mechanic). Army A commander chooses -1, and Army B commander chooses +1.

2. Significant Actions

Since we're aiming for speed, we should avoid Detailed Actions and either use the default approach, or, perhaps, skip this step entirely, if there are no PCs involved. In this case, let's just skip it.

3. Choose Battle Strategy

This is the "meat" of the system. The type of battle (pitched or encounter) may limit your choice. Essentially, these are the "maneuver" equivalents for mass combat. There is one big difference - the choice is made in secret. Army B chooses Attack - the most simple option, and Army A chooses Skirmish to exploit Fire superiority.

4. Battle Strategy Roll

Now we roll a Quick Contest of Strategy.

    Army A: Strategy-18 (16 - 1 risk + 3 Skirmish with Fire superiority); rolls a 10; MoS 8.

    Army B: Strategy-17 (16 + 1 risk); rolls a 16; MoS 1.

    Army A wins with a margin of victory 7 that gets halved to 3 due to the Skirmish strategy.

Now we look at the Combat Results Table (p. 36) and see that MoV 3 means -15% loser's causalties, -10% winner's casualties, and winner's PB shift of +1. However, due to the Skirmish strategy, there is no PB shift, and the skirmishing side takes 5% fewer casualties (i.e. 5% in this case).

From now on, Army A has -1 to Strategy due to 5% of casualties, and Army B has -3 to Strategy due to 15% of casualties.

5. Misfortunes of War

Here we roll to find out if any of PCs or major NPCs have been injured, incapacitated, killed, or captured. The target number depends on the casualties taken in this round, Risk Modifier, and some other minor things. Here we assume that only the commanders are major NPCs.

    Army A commander: MoW 4 (5 for 5% casualties - 1 risk); rolls a 9 = intact.

    Army B commander: MoW 7 (6 for 15% casualties + 1 risk); rolls a 13 = intact.

Note: How will that work on a smaller scale? On one hand, we could leave it as is to have Misfortunes of War represent major injuries due to bad luck. On the other hand, maybe this should be left out so that we determine injuries/deaths only based on the "final casualties." However, if we do that, we make the Risk Modifier have no downsides. Thus, I believe that this part should stay. Also, the injury received probably should scale with HP in the same way healing does (i.e. doubled for HP 20+, etc.). What about expenditure of other resources, such as FP, ER, and ammunition? That probably should be determined after the battle is over.

The winner still isn't clear, so we go to round #2.

Round #2

Current state: Army A - 5% casualties (-1); Army B - 15% casualties (-3); PB 0.

1. Risk

Army A commander chooses +1, and Army B commander chooses +3.

3. Choose Battle Strategy

Army A chooses Attack

Army B chooses All-Out Attack

4. Battle Strategy Roll

Now we roll a Quick Contest of Strategy.

    Army A: Strategy-16 (16 + 1 risk - 1 casualties); rolls a 12; MoS 4.

    Army B: Strategy-18 (16 + 3 risk + 2 All-Out Attack - 3 casualties); rolls a 8; MoS 10.

    Army B wins with a margin of victory 6.

Now we look at the Combat Results Table (p. 36) and see that MoV 6 means -20% loser's causalties, -10% winner's casualties, and winner's PB shift of +2. However, due to the All-Out Attack strategy, there is a +5% bonus to the loser's casualties (for a total of 25% this round), and the winner's casualties are doubled (for a total of 20% this round).

From now on, Army A has -6 to Strategy due to 30% of casualties, and Army B has -7 to Strategy due to 35% of casualties.

5. Misfortunes of War

    Army A commander: MoW 8 (7 for 25% casualties + 1 risk); rolls a 9 = intact.

    Army B commander: MoW 10 (7 for 20% casualties + 3 risk); rolls a 12 = intact.

Round #3

Current state: Army A - 30% casualties (-6); Army B - 35% casualties (-7); PB +2 for Army B.

1. Risk

Army A commander chooses +2, and Army B commander chooses +3.

3. Choose Battle Strategy

Army A chooses Fighting Retreat

Army B chooses All-Out Attack

4. Battle Strategy Roll

Now we roll a Quick Contest of Strategy.

    Army A: Strategy-15 (16 + 2 risk - 6 casualties + 3 fighting retreat); rolls a 16; MoF 1.

    Army B: Strategy-14 (16 + 3 risk + 2 All-Out Attack - 7 casualties + 2 PB); rolls a 12; MoS 4.

    Army B wins with a margin of victory 5.

Now we look at the Combat Results Table (p. 36) and see that MoV 5 means -20% loser's causalties, -10% winner's casualties, and winner's PB shift of +2. Due to the All-Out Attack strategy, there is a +5% bonus to the loser's casualties (for a total of 25% this round), and the winner's casualties are doubled (for a total of 20% this round). However, due to the Fighting Retreat strategy, Army B's casualties are halved (back to 10%), and PB shift is +3 for the total of +5.

From now on, Army A has -11 to Strategy due to 55% of casualties, and Army B has -9 to Strategy due to 45% of casualties.

5. Misfortunes of War

    Army A commander: MoW 9 (7 for 25% casualties + 2 risk); rolls a 10 = intact.

    Army B commander: MoW 9 (6 for 10% casualties + 3 risk); rolls a 11 = intact.

Round #4

Current state: Army A - 55% casualties (-11); Army B - 45% casualties (-9); PB +5 for Army B.

1. Risk

Army A commander chooses +0, and Army B commander chooses +2.

3. Choose Battle Strategy

Army A chooses Full Retreat

Army B chooses All-Out Attack

4. Battle Strategy Roll

Now we roll a Quick Contest of Strategy.

    Army A: Strategy-13 (16 + 0 risk - 11 casualties + 8 full retreat); rolls a 14; MoF 1.

    Army B: Strategy-16 (16 + 2 risk + 2 All-Out Attack - 9 casualties + 5 PB); rolls a 16; MoS 0.

    Army B wins with a margin of victory 1.

Now we look at the Combat Results Table (p. 36) and see that MoV 5 means -15% loser's causalties, -10% winner's casualties, and winner's PB shift of +1. Due to the All-Out Attack strategy, there is a +5% bonus to the loser's casualties (for a total of 20% this round), and the winner's casualties are doubled (for a total of 20% this round). However, due to the Full Retreat strategy, Army B's casualties are nullified, and Army A takes 10% fewer casualties (i.e. 10% this round).

Total casualties for Army A are 65% of casualties, and total casualties for Army B are 45%. Army A automatically loses the battle due to retreating.

5. Misfortunes of War

    Army A commander: MoW 6 (6 for 10% casualties + 0 risk); rolls a 18 = intact.

    Army B commander: none.

6. Victory?

Now, Army B's commander makes a Leadership roll. Let's assume Leadership-12. He rolls a 14, failiing the roll. This means that now we roll 1d to determine his force's reaction to the enemies retreating. I roll 1d and get a 3, which indicates pursuit. This means that Army A takes another 5% casualties and another 5% due to the Cavalry Superiority of Army B. Thus, the final casualty percantage for Army A is 75%.

After the battle, the winning side's (Army B) casualties are halved to 22.5%, rounded down to 20%. The losing side's (Army A) casualties are not recovered. Half are considered dead or dying, and the rest flee. Both commanders survive the battle.

The battlefield can be looted by Army B. GURPS Mass Combat suggests 1/5 of the cost to raise the force multiplied by its final casualty percentage. ACKS II RR suggests loot being worth one month's wages of each destroyed or routed unit. Thus, this is the entire force's monthly wage multiplied by the final casualty percentage.

Now, we have to recalculate the rosters to account for the casualties:

Army A (75% casualties)

120 Light Infantry (BR 1) -> 120 x 0.25 = 30 Light Infantry (BR ?)

120 Light Infantry (BR 1) -> 120 x 0.25 = 30 Light Infantry (BR ?)

120 Heavy Infantry A (BR 2) -> 120 x 0.25 = 30 Heavy Infantry A (BR ?)

120 Bowmen (BR 1.5, Fire) -> 120 x 0.25 = 30 Bowmen (BR ?)

Total BR: ?

Total Fire BR: ?

Army B (20% casualties)

120 Orc Light Infantry (BR 1) -> 120 x 0.8 = 96 Orc Light Infantry (BR ?)

60 Kobold Weasel Riders (BR 7, Cv) -> 60 x 0.8 = 48 Kobold Weasel Riders (BR ?)

120 Kobold Bowmen (BR 0.5, Fire) -> 120 x 0.8 = 96 Kobold Bowmen (BR ?)

Total BR: ?

Total Cv BR: ?

Total Fire BR: ?

The exact BR can be recalculated based on the individual BR of the troops, but it doesn't really matter here, so I won't bother.

Conclusion: ACKS Battle Rating can be used in GURPS Mass Combat as a substitute to Troop Strength, at least when running typical mass combat scenarios. The entire procedure I described may sound slow and unwieldy, but it does only because I have to explain everything. It's actually pretty damn quick, and if you'd like to make it even quicker, you could, for example, restrict the commanders to Attack and Full Retreat maneuvers (but that's no fun, isn't it?)

BATTLE #2 - SMALL SCALE FIGHT

All right, we found out that GURPS Mass Combat actually is great and that I might have underestimated it in the past. Let's put it to a test and try running a small-scale engagement, such as a small adventuring party fighitng off a group of goblins. The adventurers probably should win, but the players and the referee do not want to waste time playing it out second-by-second. Will it work? Here, I will be using individual BR for combatants. I will not calculate them, but use the most fitting values from ACKS II Monstrous Manual.

Side A

Fighter (BR 0.03)

Wizard (BR 0.03, Fire)

Thief (BR 0.02, Recon)

Total BR: 0.08

Total Fire BR: 0.03

Total Recon BR: 0.02

Skills: Tactics-11; Perception-11 (yes, Vision is not a skill, but you get my point)

Side B

7 Goblins (BR 0.056)

Total BR: 0.056

Skills: IQ 9; Perception-10 (and neither is IQ)

As you can see, we already run into the problem of skill/attribute substitution. Taking the Battling Monsters box into account, we know that singular monsters or small groups of disorganized monsters use the higher of their IQ and Perception in place of Strategy/Tactics. Essentially, this means that it serves as a lower limit of your Strategy/Tactics skill. The description of the Tactics skill states that it is used when you can give orders personally or through at most one other person. I'd say that when you're controlling a group of 20 or fewer people, you use Tactics. Anything higher than that is Strategy. This is more or less an asspull, so if anyone can provide me with a better number, I'm all ears.

I included Perception (or Observation, if higher) as a substitute for Intelligence Analysis for small groups for the purpose of the Reconnaissance Contest. Stealth is already accounted for in Recon Superiority. Side A have +3 due to Recon Superiority; Side B has -1 due to having no Recon elements in a land battle. Thus, Side A rolls against 14 (11 + 3) and gets a 5 (MoS 9, nice). Side B rolls against 8 (the average between Perception 10 and IQ 9 is 9.5, rounded down to 9, and -1 is for the lack of Recon elements) and gets a 12 - that's a margin of failure of 4. Thus, Side A wins with a huge margin of victory of 13.

I forgot to define the terrain, so let's assume that this battle happens in a dungeon. The Terrain and Surprise Table (p. 29) does not have such terrain, but I think it wouldn't be unreasonable to use Built-Up Areas for this purpose. Since both sides started in the dungeon, Terrain Rating is 3, not the usual 6. However, the table tells us to halve the rating again for underground environments. Rounding is not specified, so I assume that it is rounded down to Terrain Rating 1. What does this all mean? Side A's margin of victory beats Terrain Rating 1 by more than 5, so this is not surprise or initiative, but a full-blown ambush. This means that Side A can choose to fight a pitched or encounter battle, but in any case, Side B is confused on its first round. Let's fight a pitched battle.

Before the battle happens, we have to calculate the Basic Strategy Modifier. First up is Relative Troop Strength (p. 31). We divide BR 0.08 by BR 0.056 and get 1.42. This odds factor (under 1.5:1) gives no Strategy (well, Tactics) bonus here.

Then, we calculate Special Class Superiority (p. 31). Side A has a wizard that has the Fire class probably due to some offensive missile spells. Goblins have nothing like that, so Side A gets a +3 for Fire superiority. Recon Superiority does not affect combat.

Thus, Side A has Tactics 14 (11 base + 3 Fire superiority), and Side B has Perception 10.

Now we fight! Each round (1 minute in this case) will go through the same steps as before.

Round #1

1. Risk

Here, the book tells us to pick a Risk Modifier for each force's commander and any individual PC. However, one of the sides is comprised of 3 PCs, and the other has no commander. Individual PC's Risk Modifiers only play a role in Significant Actions and Misfortunes of War. Since I am suggesting to skip Significant Actions, it makes no sense to assign individual Risk Modifiers, but a general Risk Modifier for each side is still required. Side A chooses +0, and Side B chooses +0. Side B has no major NPCs or even a proper commander, so it will not suffer from Misfortunes of War. Thus, Risk Modifier should be ignored.

2. Significant Actions

We're skipping this. Come on, this is a fight against 7 goblins.

3. Choose Battle Strategy

Side A chooses Deliberate Attack for a +1 bonus. There's a special case that would let the other side switch strategies, but it doesn't apply here because Side B is confused. Speaking of that, confusion means that the only two strategies available are Rally and Full Retreat. Obviously, Side B chooses Rally - the goblins suffer -2 to their Battle Strategy roll, and at the end of the round they must make a Leadership-2 roll to stop being confused.

Note: Now wait a second. What is that were a singular monster? Would it be required to use Leadership on itself? This seems like another thing that requires adjustment. Essentially, confusion is mental stun due to surprise. Since this is abstract combat in 1-minute increments, it would be reasonable to replace it with a Will roll, possibly at a bonus if the monster has Combat Reflexes. In this specific case, however, the goblins are a group, so a Leadership roll makes sense.

4. Battle Strategy Roll

Now we roll a Quick Contest of "Strategy".

    Side A: Tactics-15 (14 + 1 Deliberate Attack); rolls a 14; MoS 1.

    Army B: Perception-8 (10 - 2 confusion); rolls a 10; MoF 2.

    Army A wins with a margin of victory 3.

Now we look at the Combat Results Table (p. 36) and see that MoV 3 means -15% loser's causalties, -10% winner's casualties, and winner's PB shift of +1.

From now on, Side A has -2 to "Strategy" due to 10% of casualties, and Side B has -3 to "Strategy" due to 15% of casualties.

Note: It feels kind of weird rolling against Perception here, but oh well. You know, Intelligence actually is accounted for in the Battle Rating calculation, so maybe it's not as strange as it seems.

5. Misfortunes of War

    Side A: MoW 6 (6 for 10% casualties)

    Fighter rolls a 11

    Wizard rolls a 11

    Thief rolls a 11

    I did not fudge any rolls, that's statistics for you. None of them suffer major injuries.

The winner still isn't clear, so we go to round #2. But before we do that, let's make that Leadership-2 roll for the goblins. Leadership is an Average skill that defaults to IQ-5. That's a harsh default! However, even if the goblins have to roll a default, they get +5 if their loyalty to one another is Good. Let's assume that it is. Thus, they roll against 7 (IQ 9 - 5 default - 2 penalty + 5 Good loyalty) and get 13, which means that they remain confused.

Round #2

Current state: Side A - 10% casualties (-2); Side B - 15% casualties (-3); PB 1 for Side A.

1. Risk

Side A chooses +0, Side B chooses +0.

3. Choose Battle Strategy

Side A chooses Deliberate Attack

Side B chooses Rally

4. Battle Strategy Roll

Now we roll a Quick Contest of "Strategy".

    Side A: Tactics-14 (14 + 1 Deliberate Attack - 2 casualties + 1 PB); rolls a 12; MoS 2.

    Side B: Perception-5 (10 - 2 confusion - 3 casualties); rolls a 12; MoF 7.

    Side A wins with a margin of victory 9.

Now we look at the Combat Results Table (p. 36) and see that MoV 9 means -25% loser's causalties, -5% winner's casualties, and winner's PB shift of +2.

From now on, Side A has -3 to Strategy due to 15% of casualties, and Side B has -8 to Strategy due to 40% of casualties.

5. Misfortunes of War

    Side A: MoW 5 (5 for 5% casualties)

    Fighter rolls a 13

    Wizard rolls a 8

    Thief rolls a 14

    None of them suffer major injuries.

Goblins roll against Leadership-7 again and get 8 (almost made it!). They remain confused. Man, getting ambushed sucks, doesn't it?

Round #3

Current state: Side A - 15% casualties (-3); Side B - 40% casualties (-8); PB 3 for Side A.

1. Risk

Side A chooses +0, Side B chooses +0.

3. Choose Battle Strategy

Side A chooses Deliberate Attack

Side B chooses Full Retreat

4. Battle Strategy Roll

Now we roll a Quick Contest of "Strategy".

    Side A: Tactics-15 (14 + 1 Deliberate Attack - 3 casualties + 3 PB); rolls a 10; MoS 5.

    Side B: Perception-6 (10 - 2 confusion - 8 casualties + 8 Full Retreat - 2 confused retreat); rolls a 14; MoF 8.

    Side A wins with a margin of victory 13.

Now we look at the Combat Results Table (p. 36) and see that MoV 13 means -30% loser's causalties, -5% winner's casualties, and winner's PB shift of +3. Due to Full Retreat, Side B takes 10% fewer casualties (for -20% total) and Side A takes no casualties at all.

The final casualties values are 60% for Side B and 15% for Side A.

5. Misfortunes of War

    None.

6. Victory?

Now, Side A's commander makes a Leadership roll. Let's assume Leadership-12. He rolls a 11, which means that he can choose to either pursue or hold the field. Let's have them pursue the goblins. This means that Side B takes another 5% casualties. Thus, the final casualty percantage for Side B is 65%.

After the battle, the winning side's (Side A) casualties are halved to 7.5%, rounded down to 5%. The losing side's (Side B) casualties are not recovered. Half (rounded up) are considered dead or dying, and the rest flee. Side B had 7 goblins. 7 * 0.35 = 2.45, rounded to 2. This means that 2 goblins are casualties. One of them is dead, and one fled (well, the other 5 fled as well, but they remain capable combatants in the future).

But what about that 5% of "casualties" for Side A? Let's assume that 100% casualties means that the victim is in 0 HP, i.e. the first unconsciousness (not death!) threshold. Thus, you simply reduce your HP by the same ratio, rounding to the nearest whole. Thus, if Fighter had HP 14, he'd lose 0.7 HP, rounded up to 1 HP. If hit location is important, roll a random one. However, this is unneccessary if the combatants in question are faceless mercenaries and not major NPCs or PCs. If that's the case, then simply note down the casualty percentage and if another abstract combat happens, your force will start with these casualties. Determine the details only if you have to switch to the personal scale (which probably is irrelevant to most NPCs, but is relevant to PCs).

What about FP loss? Fighting a Battle (p. B426) makes you lose FP if the fight lasts 10 seconds or longer. It says that realistically, any further FP loss should occur only after 2 or 3 extra minutes, and since we have 1-minute-long rounds - why not actually use these rules? Thus, if you switch to the personal scale and need the details, you lose FP based on encumbrance for every two full battle rounds. I chose two instead of three because it's easier to divide by two. As a rule, fights rarely go longer than ~4 rounds, so you even encumbered combatants shouldn't collapse from exhaustion. The fact that the winning side "recovers" half the casualties may mean that some of the "casualties" are fatigue.

However, if a particular combatant is a spellcaster or other character with combat abilities powered by FP, I suggest rolling 1d and subtracting the amount in addition to the FP loss described above. If you have ER, subtract it from it first, and then from actual FP.

If you really need to know how much ammunition or other expendable resources you've used up, use the casualty ratio.

Conclusion: It works, doesn't it? I didn't really have to mess with the system that much. So, instead of reinventing the wheel, you can take the wheel and put it on a different axis. Now you have an abstract combat system that can resolve a battle on any scale with just a few rolls. Isn't that great? Now there is no need to artificially limit yourself to personal engagements or mass combat - you can have anything inbetween, and you can have it quickly, when you need the results and not the details.

SCALING GURPS MASS COMBAT

Now I just have to consolidate the notes and write down what needs to be changed and how with small-scale "mass" combat.

1. This works regardless of whether you're using Troop Strength or borrowing Battle Rating from ACKS. I am inclined to use BR because the way it is calculated is more reasonable than when using the Heroes on the Mass Scale article to calculate TS. In addition, BR is tied to the economics systems in place rather nicely. Overall, I believe that it's an upgrade. The steps required to calculate BR may seem quite involved, especially when special abilities are concerned. I worked out a procedure that converts GURPS stats reasonably well without the special abilities (yet). But in any case, you can just estimate a good value based on the existing stats from ACKS II Monstrous Manual or ACKS II Revised Rulebook.

However, if you do use BR, you have to assign special classes from GURPS Mass Combat. In most cases, this is intuitive, but if you want more concrete guidelines, consult the Heroes on the Mass Scale article.

2. Round length for battles with less than 20 combatants on the least numerous side is 1 minute.

3. Resolution rolls have to be adjusted in the following way, depending on the number of combatants in a force.

    Forces with only a single combatant use the higher of IQ and Per in place of Strategy for Battle Strategy Rolls, and the higher of Per and Observation for Reconnaissance Contests. When using Rally, the roll is made against Will (at +2 for Combat Reflexes) instead of Leadership-2.

    Forces with 2-20 combatants use Tactics in place of Strategy for Battle Strategy Rolls, and the average between Per (or Observation, if higher) and Tactics for Reconnaissance Contests.

4. Risk Modifier may require adjustments.

    Forces that are comprised of major NPCs or PCs do not select the individual Risk Modifiers if Significant Actions are not used.

    Forces with no significant NPCs or commanders default to Risk Modifier +0.

5. Looting

ACKS II RR suggests loot being worth one month's wages of each destroyed or routed unit. Thus, this is the entire force's monthly wage multiplied by the final casualty percentage.

6. Misfortunes of War Scaling

Injury from Misfortunes of War should scale with HP in the same way healing does, i.e. doubled at 20-29 HP, tripled at 30-39 HP, and so on.

7. Casualties for Individual Characters

If a major NPC, PC, or other character is a separate combat element, the casualty percentage defines the percentage of HP lost (round to the nearest whole number). The same ratio can be used to determine how much ammunition or other expendable resources was spent.

Each two full rounds of combat make characters lose FP as per Fighting the Battle (p. B426).

If the character is a spellcaster or has other combat abilities powered by FP, roll 1d and subtract that amount from the FP score in addition to the FP loss described above.

And that's it. I may have missed something, but if that's the case, I will edit this post later.