Abstract Combat in OD&D/FMC

Combat in OD&D is different than from subsequent editions of D&D. Characters make one attack per hit die they have, against “man-sized” opponents (though some have argued there is no reason not to extend it to all opponents, “man-sized” or not). Thus, a troll who has HD 6+3 makes six attacks (one of which with a +3 to-hit bonus). This system is more “fast and furious” than the one that appeared in Greyhawk which has vastly reduced numbers of attacks, but it is unintuitive, complex, and does not scale. It is no wonder that Gygax switched to the system we see today, but one has to admit there is an appeal in making combat faster.

I have a specific motivation in interfacing semi-mass “skirmish” combat with individual combat, allowing players to have a handful of characters without making attack rolls for each. My friend Jenx of Gorgon Bones has been trying to figure out a skirmish combat system for his OD&D campaign, and has tried using the warband system from Errant to accomplish this. Since he didn’t care for how it worked out, I wanted to suggest this as something grounded in OD&D’s existing terms.

The basic premise of this post is that if a level # fighter fights as # regular figures, then # regular figures can be treated as a level # fighter. I also suggest giving all characters +1 damage for each hit die they have, rather than making a number of attacks equal to their hit dice.

It is assumed that fighters and monsters get +1 on attack rolls per HD or per level (with mook monsters like skeletons or kobolds getting +0). This is unlike OD&D as written, but is a fairly standard convention.

The Issue

As I said above, combat in OD&D does not scale. Let’s take the above chart as an example, which approximates that a monster with # HD has a bonus equal to # on attack rolls. The result is that high-level monsters deal obscene amounts of damage. For example, a 10 HD giant deals on average 26 damage against another giant (AC 4). That is 74% of the average giant’s hit points and, more importantly, takes 10 rolls to resolve.

Combat in OD&D as written is also restricted to one-versus-one combat, whereas the recommended Chainmail system supports mass combat. Although later D&D altogether deemphasizes mass combat perhaps because of the original limitations of OD&D, OD&D itself does not.

Fighters as Abstraction

Let’s set one rule to start with: # regular figures can be treated as a level # fighter. This is the inverse of the common understanding that a level # fighter fights as # regular figures (although, in OD&D, this is not limited to fighters). By taking the inverse of this earlier rule, we can abstract a good handful of “regular-sized” monsters or mercenaries as a single unit with decent strength in numbers.

This means that when you have a group of 4 orcs, you can abstract them as a level 4 fighter in order to attack or defend against another character. Hiring 10 mercenaries is equivalent to hiring a level 10 fighter. You can even split units on the fly, if so desired, such as when wanting to attack multiple targets or risk multiple attack rolls instead of one (e.g. a level 10 fighter can make one level 10 attack, or two level 5 attacks).

This is preferable to rolling eight attacks each, for 4 orcs versus a level 4 fighter.

Mooks & Minions

I think that HD 1/2 monsters like kobolds and skeletons should be like half a fighter, such that 8 kobolds fight as 4 “regular-sized” creatures or as a level 4 fighter. In general, I don’t like that kobolds are defined as HD 1/2 while goblins are defined as HD 1-1; I feel like they should both just be HD 1/2.

Halflings & Missiles

Remember the Chainmail rule, imported into OD&D, that 2 halfling archers count as 3 for the purpose of mass combat? That can be implemented directly into this rule! 2 halfling archers can shoot as a level 3 fighter, or a level 4 halfling can shoot as a level 6 fighter (which almost makes up for level 4 being their maximum).

Hydras’ Heads

From Fantastic Medieval Campaigns, p. 80: “Hydras of five heads fight as fifth level fighters, six heads as the sixth level, et cetera.” Isn’t this much more intuitive in the context of fighters as an abstraction of many troops or, in this case, the many heads of a hydra?

Tight Corridors

Apparently, three figures can fit "abreast" in a ten-foot corridor. I think this serves as a reasonable limitation on unit sizes, at least in the context of a dungeon.

+1 Damage Per HD

A second rule: each HD gives +1 damage per attack. This may seem like a lot relative to modern OSR sensibilities, but is significantly less than the damage quantities expected in OD&D as written. Our 10 HD giant from earlier now deals 1d6+10 damage on a successful attack, and our party of 4 orcs deals 1d6+4 damage. This creates a natural tradeoff between making a more powerful attack, or multiple weaker attacks.

The basis of this rule is a certain convention, explained in the OD&D guidebook Muster, that monsters deal a quantity of damage that is (sort of) logarithmic compared to their HD. For example, a 4 HD monster deals 2 dice of damage, while an 8 HD monster deals 3 dice of damage. This is a nice convention that aligns neatly with what we expect from monsters of these levels, but it relates less to OD&D than to how it interfaces with Chainmail.

Giving +1 damage per HD is approximate to the above rule from Muster while remaining strictly within OD&D’s terms. It requires no interfacing between the expectations of Chainmail and those of OD&D. Simply add HD, without bonuses or conversions, to the damage roll. Below are examples:

• Kobolds add +0.
• Orcs add +1.
• Gnolls add +2.
• Ogres add +4.
• Trolls add +6.
• Giants add from +8 to +12 depending on their HD.

Below is another table showing average damage per HD. Notice that if you split a unit into two halves, or split one attack into two equal ones, you deal slightly more damage on average. For example, one HD 8 attack deals ~10 damage against no armor, but two HD 4 attacks deal ~11 damage because of the potential additional damage die. It's not a big deal, but maybe still notable. More fun is that, on average (with respect to AC), each monster typically deals damage equal to their hit dice. Now that's nice!

I think this change would complement another that I won’t shut up about: define HD 1/2 as having 1d6 HP, and give everyone else an extra 1d6 HP. Although what brought that on was thinking about Arneson, such a change would probably feel less like OD&D. Which is why I’m hiding it in a paragraph here! It’s besides the point of all this.

Conclusion

This system restates the existing distinction between “regular” and “fantastic” units, except that it does so within the logic of OD&D’s own terms instead of being in reference to Chainmail. The distinction is also an “imaginary” one rather than a formal one: does a given unit represent a high-level character, or an aggregate of many low-level characters? It doesn't matter, rules-wise! The math is the same either way.