Monday, January 10, 2011

Basic D&D: Chainmail Conversions


OD&D is, of course, based heavily on the Chainmail Fantasy miniatures game. In fact, it is included as recommended equipment (Vol-1, p. 5; in the same category as dice and OD&D itself) and it is incorporated by reference at numerous points (e.g., Vol-2, p. 5: "Special Ability functions are generally as indicated in CHAINMAIL where not contradictory to the information stated hereinafter...").

You probably know that Chainmail's man-to-man and fantasy combat mechanics functioned by way of 2d6 rolls, whereas OD&D's "Alternative Combat System" functions by way of the ubiquitous d20. Therefore, as is obvious to pretty much anyone who's looked at it, the modifiers that appear in Chainmail would have very different effects probability-wise, if used verbatim within the core D&D system.

Intuitively speaking, a conversion from Chainmail to OD&D should more-or-less double any modifiers, in that Chainmail's 2d6 roll has a range of about 10 (11, really) and OD&D has a range of 20. But in addition to that, Chainmail's non-uniform distribution varies from point to point. Look at the table above for specifics: depending on where the initial target for success was, a +1 bonus in Chainmail might be the equivalent of anywhere from 1/2-point to over 3 points in D&D. On average, however, a +1 Chainmail bonus is worth +1.82 D&D bonus (i.e., 20/11; but easily rounded up to +2, as expected).

Nevertheless, the real issue I want to highlight is this: Throughout the entire publication history of OD&D, AD&D, d20 System, etc., the precedent was established to translate Chainmail-defined bonuses on a direct 1-for-1 basis (i.e., entirely overlooking this issue). Here are some examples:
  • Goblins, kobolds, and orcs. Per Chainmail, "When fighting in full daylight or bright light they must subtract 1 from their Morale Rating, as well as 1 from any die rolled" [CM p. 29-30]; in OD&D, this translates to an identical, "when they are subjected to full daylight they subtract -1 from their attack and morale dice." [Vol-2, p. 7]. Likewise, this same modifier is carried forward into later editions [AD&D MM p. 47, et. al.]
  • Weapon-vs-armor. Taking a single sample row from the weapon-vs-armor types in Chainmail, we see target numbers for a hand-axe of "7/7/8/9/10/10/11/12" [CM p. 41]; in the Greyhawk D&D supplement we see hand-axe modifiers of "+1/+1/0/0/-1/-1/-2/-3" [Sup-I, p. 13]. This is fundamentally the same progression, converting CM targets of 8 or 9 to +0, and any pips above/below that on a 1-for-1 basis. In fact, this is true for the entire OD&D weapon-vs-AC table, which is then copied forward to AD&D with only minor adjustments (for example, the hand axe modifiers are identical except for a single pip difference at AC4). [AD&D PHB p. 38].
  • Missile fire. In the Chainmail man-to-man missile fire table, a target progression of -2/-1/0 is shown for each range category of short/medium/long [CM p. 41], and this coverts 1-for-1 to the D&D to-hit rule of +2/+1/0 [Vol-1, p. 20]. However, in AD&D this was wisely altered to become 0/-2/-5 [AD&D PHB p. 38].
  • Mounted combat. Per Chainmail, "When fighting men afoot mounted men add +1 to their dice for melees and the men afoot must subtract -1 from their melee dice" [CM p. 26]. While this rule wasn't transcribed into the OD&D or AD&D core books themselves, it is copied unchanged into places such as the 1E AD&D Wilderness Survival Guide [WSG, p. 86], 2E AD&D [DMG, "Mounted Combat"], and 3E D&D [3E PHB, p. 138].
  • Parrying. For lighter weapons, Chainmail provides the ability to parry, "subtracting 2 from the attacker's roll" [CM p. 25-26]; this is copied without change into Holmes Basic D&D: "The parry subtracts 2 from the attacker's die roll" [Holmes D&D p. 21].
  • Magic swords. In Chainmail fantastic combat, "they give a plus 1 to the dice score... Excaliber [sic] and other 'Super Swords' would give a plus two or three!"; and in OD&D we also see magic swords from +1 to +3 in value [Vol-2, p. 23]. That said, in AD&D swords were expanded from +1 to +5 in value [DMG p. 124], and Arthur's sword was in fact later given the maximum +5 bonus [AD&D DDG, p. 18].
So, if you aim to use OD&D by itself, and include by reference the details on man-to-man combat that appear only in Chainmail (such as several bullet-points above), then you've got a somewhat uncomfortable dilemma to resolve. You need to either (a) use the modifiers as written (1-for-1), and thus greatly minimize the originally-designed probability effects, or (b) convert the modifiers (2-for-1), and thus violate the by-the-book rules in OD&D, AD&D, et. al., on each of these issues (and more generally, the overall precedent for such translations).

What would I want to do? Personally, I think I prefer option (b). I'm willing to chalk up these 1-for-1 translations as fundamentally an oversight and a "mistake" in D&D, and consider a more faithful conversion in probability on a 2-for-1 basis. In addition, I might make the philosophical case that no 1-point situational modifier is worth the mental effort to track. For example, if someone has a +1 Strength bonus to all melee attacks (such that it can be included on the PC card), then by all means, use that. If a weapon-vs-AC effect, or a special skill or ability, gave +2 in a given situation, then that is worth tracking. But tracking fiddly +1 sometimes-modifiers makes a difference so rarely, that it's better to entirely avoid. (3E "Bard Song": I'm looking at you and your ilk.)

In fact, this overall philosophy matches those modifiers that were freshly introduced at the time of AD&D. Cover modifiers are given in increments of at least +2 (cover AC +2/4/7/10; DMG p. 64). The bonus for charging is set at +2 (DMG p. 66). Special to-hit bonuses are in increments of +2 (opponent off-balance +2; opponent stunned or slowed +4; DMG p. 67). Likewise, if I have a shortcut system that generates results within 1 pip of the official tables (such as Target 20: see sidebar), then in my games I'm happy to call that "close enough". In short, I might argue: Situational modifiers in D&D should be at least +/-2 to be worth bothering with. And this is synchronous, I think, with the desire to double Chainmail modifiers if we opt to use them within D&D.

What's your preference? Poll results here.

15 comments:

  1. This is a very insightful post. Thanks for making (and, no, I'm not sure what my stance is on it -- I need to think some more).

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  3. Great post. You're overlooking/conflating one aspect--which is what gygax and co. did as well. That is between normal combat and fantasy.

    Taking magic swords and armor; in normal man-to-man combat a sword really adds +3 (+1d6 actually) to the 2d6 attack roll, but only +1 pip on the FCT.

    The magic armor grant -3 to the 2d6 attack roll in normal MtM but only -1 on the fantasy MtM (aka FCT).

    This is easily chalked up to the fact that the FCT 2d6 attack represented 1 hit = 1 kill (or more accurately a single roll that determined an entire battle) so any small bonus was important, but a hero could withststand up to 4 simultaneous hits in normal man-to-man combat before being brought low, so the modifiers could be larger.

    This is evidenced in the magic arrow rules as well. In normal MtM a 'magic missile' automatically struck it's target, but in fantasy MtM/FCT the magic arrow only provided a +1 to the 2d6 roll.

    I lean toward the larger numbers, but at 1st level characters are still in that 1 hit 1 kill boat.

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  4. What I'd really like to do sometime is us the Man-to-Man combat charts with a d12 for D&D. It would flatten the curve a bit compared to Chainmail proper, and makes any bonus somewhat more profound than in D&D proper, but the idea appeals to me. I think I'd like to rate weapons by their attack rank rather than by damage dealt.

    And anybody who has a whole mess of d12s would be able to quickly roll for several henchmen or several monsters at once, more easily than rolling a bunch of d20s, IMO.

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  5. If we don't track 1-point modifiers, I'm not sure there's a good reason to use a d20 at all. Using a d10 or the lovely little d12 might be a better choice, halving all AD&D modifiers (and ignoring the difference in a d12 just because it's a cool die).

    In the system I use, with a d20 for success checks, inconsequential modifiers (the sun was in my eyes!) are ignored. Important modifiers give a +/- 1 or 2 (mounted, attacked from behind, Orcish sunlight sensitivity, blindness, parrying). This way there's a large swath of probability but modifiers don't affect it to the point that it becomes a certainty.

    This is a problem in games like AD&D where the maximum Armor Class is only 20 pips away from the lowest Armor Class. A high level Fighter with weapon specialization, a good magic weapon, high Strength, and other magic items may reach a point where he misses any target only on an unmodified 1. This seems funky when you consider his chance to fail is the same whether he tries to pierce a dragon's scales or smack any part of a barn.

    D&D 3E sort of fixed this with unlimited target numbers (both at the low end and the high end) but combined that with inflated number values on all sides so everything was more difficult to track at the table.

    ---

    How possible do you think it is that the game designers just decided to reduce the effect of modifiers by keeping them small while increasing the die roll's probability space? Looking at it like you did it does seem unlikely. A simpler answer is just that the writers were a little lazy and didn't bother to check the probabilities. But didn't Gygax have a significant hand in the 1E AD&D DMG? Wouldn't he have taken that into account?

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  6. Hey 1d30 -- I do think that +1 modifiers are fine and useful granularity if they're fixed on the sheet (Level, AC, Strength bonus, etc.). It's situational +1 modifiers that I'd like to clear out.

    At this point my top historical hypothesis is what you call the "lazy" one; same for issues of man-to-man scale, etc. Gygax & others of the original D&D crew were (and are) quite public about how unconcerned they were with such trivia (to them).

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  7. Odrook said:
    'What I'd really like to do sometime is us the Man-to-Man combat charts with a d12 for D&D'.
    The problem with this approach is that so much of the static numbers that represent the power of units in Chainmail are in that mid range, i.e. a knights morale and his chance to remain. If the probability were not bell-shaped the system as presented would not really work; a d12, unfortunately makes the result too random.

    Delta wrote:
    "It's situational +1 modifiers that I'd like to clear out".
    Should the assassin receive +8 when attacking at the rear?

    "(a) greatly minimize the originally-designed probability effects, or (b) convert the modifiers (2-for-1), and thus violate the by-the-book rules in OD&D, AD&D, et. al., on each of these issues (and more generally, the overall precedent for such translations)".
    I tried this and got into a lengthy discussion about it in the OD&D forum at K&K. I discovered that one could alter the modifiers as you suggest. However, the really dilema came with the curviture and distribution of probablitity that to my mind, just make Chainmail and all of its D&D derivatives to be just entirely different games. You may be right in your summing this up as 'laziness', but I also think to expand the granularity of the game the curviture had to be altered and that included blunting the effect of the modifiers, rightly or wrongly.

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  8. Hey sepulchre -- Of course, I'm just talking here about modifiers that first appear in Chainmail. The +4 assassin rear attack in the AD&D PHB seems fine to me.

    You might also note that a very few things did get design attention such that they did evolve between Chainmail & AD&D. Examples: (1) Rear attack +1 [CM p. 25] becomes rear attack +2 [AD&D DMG p. 70]. (2) Missile ranges 0/-1/-2 [CM p. 41,OD&D Vol-1 p. 20] becomes 0/-2/-5 [AD&D PHB p. 38]. (3) Magic sword bonuses +1 to +3 [CM p. 38, OD&D Vol-2 p. 23] becomes +1 to +5 [AD&D DMG p. 124].

    So I think that to whatever extent the designers overcame their "laziness" (to use 1d30's phrase), they did go in a direction of doubling modifiers from Chainmail, which I think is correct.

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  12. Delta wrote:
    'just talking here about modifiers that first appear in Chainmail'.

    Got it. Yeah I didn't mean to sound cheeky about the assassin, and I see your point the modifier to attacks from the rear becomes +2in AD&D. I just found so much of the seeming disconnect between the two systems really frustrating when trying to distill what the game (something based in Chainmail with the some of the example of granularity as it appeared in OD&D derivatives and even AD&D) might really have been at one time, or just ideally.

    "Examples: (1) Rear attack +1 [CM p. 25] becomes rear attack +2 [AD&D DMG p. 70]. (2) Missile ranges 0/-1/-2 [CM p. 41,OD&D Vol-1 p. 20] becomes 0/-2/-5 [AD&D PHB p. 38]. (3) Magic sword bonuses +1 to +3 [CM p. 38, OD&D Vol-2 p. 23] becomes +1 to +5 [AD&D DMG p. 124]".

    Hey, thanks for the examples and source texts too. Indeed, those changes seem to follow and imply some edition-cohesion in design.

    "In fact, this overall philosophy matches those modifiers that were freshly introduced at the time of AD&D. Cover modifiers are given in increments of at least +2 (cover AC +2/4/7/10; DMG p. 64). The bonus for charging is set at +2 (DMG p. 66). Special to-hit bonuses are in increments of +2 (opponent off-balance +2; opponent stunned or slowed +4; DMG p. 67)."

    Okay, I see, so it is your assertion that by the publication of AD&D there is pretty much an even translation of the Chainmail modifiers. Did you find any situational modifiers in AD&D that were overlooked? I am thinking of your example of the goblins in sunlight. In Chainmail that modifier is a total of -2 (-1/die) and in OD&D and AD&D it is -1. There are other modifiers in AD&D that appear this way but do not bear a direct relationship to Chainmail, i.e. fanaticism (see dervish). Should the goblin, or even the dervish [who has +1 to hit against normal men (1st-3rd lvl.in OD&D, expanded or overlooked in AD&D to include all)], then be translated as -2 in daylight?

    Great post BTW, thanks!

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  13. Ok this is the 2nd time this has happened.

    Delta why are you deleting my posts? I certainly did not.

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  14. Hey sepulchre, yeah, I think we're on the same wavelength with all your latter comments. I think all the "other stuff" from my original post counts as being overlooked for this kind of fix. Namely -- goblins in light; weapon-vs-armor; mounted combat; and parrying. All that stuff was just directly copied forward (where it appeared) without any modification.

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  15. UWS Guy, I don't mean to be a jerk, as often you have the kernel of a good point, but -- your posts tend to be really long and kind of garbled and I think they derail the flow of conversation. I feel like I need to ask that your future comments be more concise and to the point. Regards, DC.

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