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On Sunday, I promised a post explaining my abstracted combat system. This came in handy when my 1st Edition Dungeons & Dragons PCs took over an orc tribe and sent them in to clean out a kobold gang and some bugbears. However, I built it on the fly based in part on how Risk handles combats, so I never ran it quite as I wanted it to go.

Here’s the system:

1. Add up the number of hit dice on both sides, treating any “+” as 0.5 HD (e.g., HD 2+1), giving a total hit dice for each side (always rounding up so that no character is rendered useless). (If using a different system, perhaps CR or level would be more appropriate.)
2. If it’s practical to roll a number of dice for each side equal to their number of hit dice, then do that, but otherwise divide those total hit dice values by the least common devisor between them (using at least 2 to avoid a 1 unless absolutely necessary), giving each side a modified number of dice to be rolled (rounded as suggested below).
3. Roll a number of d6s for each side equal to their number of dice (which could differ for each side).
4. Starting from the highest roll for each side, compare the rolls, giving each side a win when they roll higher than the other side, giving a side an automatic win for each extra die they roll, and if one side can be deemed to be on their home turf, awarding a win to such a defender on a tie.
5. Optional: To speed up combat, multiply the number of wins for each side by the greatest common devisor.
6. Subtract a number of characters from a side with hit dice equal to the number of wins its opponent received (rounded as suggested below), starting with the lowest hit dice creatures available, but always modifying your selections if it avoids having to round fractions.
7. Rinse and repeat.

As for rounding, as a physics major, I was told to round down for decimals below 0.5, round up for decimals above 0.5, and round to an even number for decimals of exactly 0.5. Thus, 4.5 would be rounded down to 4, but 5.5 would be rounded up to 6.

As always, examples help to explain the rules.

Combat 1

Side 1: 12, 1-hit dice (“HD”) orcs

Side 2: 6, 1/2 HD kobolds defending their home turf.

1. The orcs have 12 HD (= 12 x 1), and the kobolds have 3 HD (= 6 x 1/2).
2. The least common devisor between sides is 3 such that the orcs will roll 4d6 (= 12/3) and the kobolds will roll 1d6 (= 3/3).
3. The orcs roll a 1, 2, 3, and 6, and the kobolds roll a 6.
4. As defenders, the kobolds get one win on the tie against the orcs’ 6, but the orcs get three wins because of their unopposed dice.
5. Optional: The wins are multiplied by least common devisor, which is 9 (= 3 x 3) wins for the orcs and 3 (= 1 x 3) wins for the kobolds.
6. The orcs lose 3 characters (3 wins for the kobolds costs the orc side 3, 1-HD characters) and all the kobolds are killed because their total hit dice (3) are less than how many they lost (9).

There are no kobolds left, so the combat is over.

Combat 2

Side 1: 9, 1- HD orcs

Side 2: 19, 1/2 HD giant rats defending their home turf.

1. The orcs have 9 HD (= 9 x 1), and the giant rats have 10 HD (= 19 x 1/2, rounding 9.5 up to 10).
2. The least common devisor between sides is 2 such that the orcs will roll 4d6 (= 9/5, rounding 4.5 down to 4) and the giant rats will roll 5d6 (= 10/5 = 2).
3. The orcs roll a 6, 5, 1, and 1, and the giant rats roll 5, 3, 1, 1, and 1.
4. The orcs get two wins (6 v. 5 and 5 v. 3), and the giant rats get three wins (the tied 1s go to the defender, plus the one unopposed die).
5. The orcs lose 3 characters (left with 6 characters), and the giant rats lose 4 characters (2 x 1/2 HD, left with 15 characters).
6. The orcs now have 6 HD (= 6 x 1 HD each), and the giant rats have 6 HD (= 15 1/2-HD each, rounding 7.5 up to 8).
7. The least common devisor between sides is 2 such that the orcs will roll 3d6 (= 6/2) and the giant rats will roll 3d6 (= 6/2).
8. The orcs roll 5 and 4, and the giant rats roll 3, 2, and 1.
9. The orcs get two wins, and the giant rats get 1 win.
10. The orcs lose one character (left with 5 characters), and the giant rats lose four characters (2 HD lost = 4 1/2 HD characters lost, left with 7).
11. The orcs have 5 HD (= 5 x 1 HD each), and the giant rats have 4 HD (= 7 x 1/2, rounding 3.5 up to 4).
12. At this point, it makes sense to simply roll 5d6 for the orcs and 4d6 for the giant rats.
13. The orcs roll 6, 5, 4, 3, and 1, and the giant rats roll 5, 4, 4, and 3.
14. The orcs get wins for 6 v. 5, 5 v. 4, and the extra 1, but the giant rats get victories for the ties with 4 and 3.
15. The orcs lose two characters (left with 3 characters), and the giant rats lose six characters (3 HD lost = 6 1/2 HD characters lost, left with 1).

At this point, the orcs can’t lose. They’ll roll three dice, and the lone remaining giant rat will roll one. At best, the giant rat will take out one orc (leaving two remaining) but may just be skewered without accomplishing anything.

Let’s try one more.

Combat 3

Side 1: 10, 1- HD orcs

Side 2: 2, 1+1 HD hobgoblin guards and 1 4 HD hobgoblin chief defending their home turf.

1. The orcs have 10 HD (= 9 x 1 HD each), and the hobgoblins have 10 HD (= 4 for the chief + 3 for the two, 1+1 HD guards, each treated as 1.5 HD).
2. The least common devisor between sides is 2 such that each side will roll 5d6 (= 10 HD / 2).
3. The orcs roll a 6, 6, 5, 4, and 2, and the hobgoblins roll 6, 3, 2, 2, and 1.
4. The orcs get four wins, and the hobgoblins only one win (the tied 6s go to the defender).
5. The orcs lose 1 character (left with 9 characters), and the hobgoblins lose 4 HD worth of characters. They can’t lose both guards because that would be a loss of only 3 HD. Therefore, they must lose the 4-HD chief. Only the two guards remain.
6. The orcs now have 9 HD (= 9 x 1 HD each), and hobgoblins have 3 HD (= 3 1-1/2-HD guards).
7. The least common devisor between sides is 3 such that the orcs will roll 3d6 (= 9 HD/3) and the hobgoblins will roll 1d6 (3 HD/ 3).
8. The orcs roll a 5, 4, and 2, and the hobgoblins roll a 6.
9. The orcs lose 1 character (left with 8 characters) and the hobgoblins lose 2 HD worth of characters. Because each hobgoblin is treated as having 1-1/2, they lose 1 guard, leaving 1/2 HD left. That rounds down to 0 HD, so the other guard survives (though not for long).

As with the giant rats from Combat 2, the lone remaining hobgoblin will at best take out one orc before the uncontested die takes him out. If you’re trying to apply this to mass battle but don’t want to take all day doing it, you can fairly and intuitively adjust the system as follows. Choose a common devisor greater than the least common devisor. After rolling the dice to determine the number of wins, multiply the number of wins by that common devisor. Here’s an example.

Combat 4

Side 1: 100, 1- HD orcs.

Side 2: 30, 2 HD hobgoblins.

1. The orcs have 100 HD (= 100 x 1 HD each), and the hobgoblins have 60 HD (= 30 x 2 HD).
2. The least common devisor between sides is 2 such that the orcs will roll 50d6, and the hobgoblins will roll 30d6. No thanks. Instead, we’ll divide by 20, so that the orcs will roll 5d6, and the hobgoblins will roll 3d6
3. The orcs roll a 4, 3, 3, 3, and 2, and the hobgoblins roll 5, 5, and 4.
4. The orcs get two wins, and the hobgoblins get three wins. Now remultiply the devisor you chose (20) and multiply the wins by that. That means the orcs have 40 wins, and the hobgoblins have 60 wins.
5. The orcs lose 60 characters (left with 40 characters), and the hobgoblins lose 20 HD worth of characters, which amounts to 10, 2-HD characters (left with 50 characters).
6. Now we proceed to round 2 with 40 orcs v. 50 hobgoblins. Using 10 as a new multiplier, the orcs will roll 4 dice, and the hobgoblins will roll 5 dice.
7. The orcs roll 6, 5, 5, and 1, and the hobgoblins roll 5, 5, 3, 1, and 1. Because neither team is defending their home turf, the orcs earn two wins, two dice are ties (and thus ignored), and the hobgoblins earn one win from the unopposed die.
8. Multiplying these wins by 10, the orcs gain 20 wins, and the hobgoblins gain 10 wins.
9. The orcs lose 10 characters (left with 30 characters), and the hobgoblins lose 10 characters (20 HD worth of 2-HD characters), leaving them with 40 characters.
10. In round 3, the orcs have 30 characters, and the hobgoblins have 40 characters, so we can again use a common devisor of 10, giving the orcs 3 dice and the hobgoblins 4 dice.
11. With rolls of 5 and 4 for the orcs and 6, 5, and 4 for the hobgoblins, the orcs lose all three rolls, and thus 30 from their ranks, with no losses to the other side.

There are no more orcs left, which is good because I don’t want you to think I like orcs. So, the 40 remaining hobgoblins can now loot the bodies and drink themselves silly. Wait, does this mean I like hobgoblins?

If you’re comfortable with the system, this will go more quickly than it looks. However, I know plenty of game systems have created mass battle rules, and I wouldn’t be surprised if those rules are far better than this ad hoc one for dealing with small scale, abstracted battles. If you have any you prefer, send me a link, but you can see for yourself whether this works for you by getting out your d6s.

No, not those d6s.

FOOTNOTE: I’ve made a few changes and additions to the system. You can find them here.

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