Armor as Damage Reduction?

An obvious refinement in handling armor in RPGs is making armor reduce damage instead of the original D&D reducing the chance of taking damage.  Intuitively that’s what armor does, right?  It doesn’t make you better at dodging, it just reduces how much you get hurt when you get smacked.   A lot of pretty good games over the years have taken that tack, including one of my favorite combat systems, the microgame Melee that formed the basis of The Fantasy Trip and later on GURPS.

The thing is, the phrase “roll to hit” is a misnomer.  It’s really roll to hurt.  We don’t, except in some special circumstances, really care if the blow missed completely or hit the armor and bounced off.  What we want to know is if the blow actually hurt enough to bring the foe closer to defeat.  From there it’s easy to see that the “space” of possible results from an attack are basically the same whether you treat armor as reducing the chance of rolling for damage or reducing the damage once rolled: the target isn’t hit at all, the target would have been hurt but for armor, and the target is hurt. Editions of D&D with rules for “touch attacks” only needing to beat the AC of an unarmored man make this explicit… really any attack that would have hit an unarmored man but didn’t beat the AC of the target can be presumed to have hit but failed to penetrate the armor1.

In fact, the only real difference between the two approaches is that armor as damage reduction introduces an extra oddity that usually needs to be addressed. In the standard D&D AC system armor can make it unlikely that a blow scores a wound, but a blow that finds a chink in the armor can be just as deadly to an armored man as an unarmored man: an arrow to the eye slit2 will kill a knight just as dead as a peasant. In contrast, in systems that use armor as DR it’s often the case that once you have a reasonable amount of armor, it becomes literally impossible for a single blow to kill an average man.  If an arrow does 1d6 and chain armor stops, say, 4 points, then a first-level fighter with at least 3 HP can’t ever be killed with a single arrow.

To compensate for this, DR systems almost always add further complication.  Typically they include “critical hits” that introduce the possibility that if you roll well the damage is then multiplied by some factor large enough for weapons to once again pose a deadly danger to the average man.  Others will introduce things like differentiation between weapons that can pierce through the armor and weapons that will bounce off, so an arrow or warhammer might be more dangerous to a heavily armored fighter than a club or saber, or  add “called shots” so that if you want to actually hurt a knight in plate armor with your arrow you have to take a penalty to the roll representing aiming for the eye slit. Which is all well and good, but wouldn’t actually be necessary if you hadn’t introduced the complication of damage reduction in the first place.  It’s several extra steps to get back to “against heavy armor you need to get extra lucky or good if you want to do significant damage.”

When I was younger I used to heavily favor such complications; it’s only comparatively recently that I’ve come around to preferring the simpler “chance to hurt” abstraction.  I still enjoy me a good critical hit, but I like ’em like Dungeon Crawl Classics or Arduin, where they are used to add a big dollop of flavor with results that are more specific and usually much grittier than a straight double hit point damage.  In a system where damage is usually abstract: 3 points, 4 points, 8 points, it’s nice to have the occasional “your ear is torn off” or “your forearm is shattered” as long as it doesn’t become something you have to calculate every blow.



  1. and when it comes to simulation, that’s probably a more accurate representation anyway.  Most of the time if you’re hit while wearing armor you won’t take the same wound that an unarmored person would take, except shallower. If it didn’t find a weak point in your armor chances are you won’t take any damage at all, what damage you do take will often be in the form of a bruise or broken rib instead of a gash or hole in your flesh. The only game I can think of off-hand that did that level of  simulation was CORPS, which took the physics-based intuition even farther and made armor reduce some damage, and then convert some of the remaining damage into less lethal concussion damage.  Of course, at the level of abstraction Hit Points represent you could/should simply interpret differing amounts of damage as representing different levels of wound anyway, but if you’re doing that there’s even less reason to care whether “no damage” is a 13 on the to-hit roll vs AC 14 or a 10 on the to-hit roll vs AC 10 but a 3 on the damage die against 4 points of DR. 
  2. a reasonable interpretation of rolling high damage against an armored knight, even if there’s nothing explicit in the mechanics dictating that’s where it hit. 

8 thoughts on “Armor as Damage Reduction?

  1. Nathaniel Lussier says:

    I am in the process of writing a system (I know, who isn’t…) and I have been struggling with how to handle this as well. Part of my struggle though is I am trying to get away from hit points, or minimize their use. They are useful yes, but if you have a system where as you level up, you just keep getting more, you end up like high level dnd where half of everything you fight is no real threat, and it turns into the poke the giant toe with little swords of mighty damage until you kill something.

    I have tried couching the hit points as endurance, or “luck” but I have watched every group just default into treating them as wounds.

    So the challenge I faced was how do I include armor in a system where damage is tracked, not by points, but by effect on the body part. It means I have to establish where the armor covers, and such. (This is, afterall, why hit point abstraction is used. Just look at the complications of balance in Warthunder vs World of Tanks for more illustrations of that complication.)

    I don’t have an answer yet, but I will… it is only a matter of time. Your entry though shows that I am not alone in rethinking armor though, and I agree with your points, especially as I have gotten some experience taking hits in some of this armor.

    I have worn full plate armor, and sparred in it. I learned early on that unless I have a shield, there is not point trying to avoid a hit, most of them glance off and I will not feel a thing, and glancing hits in most scored sparing systems do not count. You have to land and hold.

    I never even felt most of the hits outside of a dull thudding vibration.

  2. Douglas Cole says:

    Dragon Heresy is using Armor as DR, and I think I’ve found a satisfactory solution to Nathaniel’s wounds vs other things issue as well. The rules are written (200,000 words of ’em), and now just have to finish up the monster descriptions, then The Book of Deeds, the campaign book, will be done.

  3. Professor Oats says:

    “It’s really roll to hurt.”

    Been saying this for years. I like to call Armor Class a lossless abstraction* because all of its parts are there to be sussed out if you need to make a ruling (touch attacks being a codified example). The one area where things get tricky — and I don’t think I’ve seen anyone point this out before — is with modifiers based on Strength. A giant could pulverize your armor, but he shouldn’t be nabbing fairies like Mr. Miyagi, so we need another ruling. Seems we should first make a touch attack sans strength bonus; if it succeeds, then add the attacker’s strength bonus and the defender’s armor bonus into the equation to see if it actually hurts. Not the most elegant rule, but it works

    * Hit points are an example of a lossy abstraction. They work so long as you don’t examine ’em too closely

    • Professor Oats says:

      Crap, I forgot Miyagi struggled to catch a fly with chopsticks. In my defense, I haven’t seen The Karate Kid in some years

      • Joshua Macy says:

        I’d be inclined to rule that when there’s a big enough size difference, the combatants aren’t actually “in melee” so things like strength bonus, free attack when opponent disengaged or even having to stop don’t apply. But if anything AC bonuses for tiny foes and penalties for huge ones are easier to handle than adjusting DR.

  4. kleefaj says:

    I never thought of it or heard it put that way: “roll to hurt”.

    I started out with Holmes when I was a young’n, then AD&D, then Melee and The Fantasy Trip. DR in Melee and TFT seemed to make more sense to me. I play GURPS now and play T&T solos and am looking to start DM’ing (one or all of T&T, LotFP, DCC). I was just going to accept Armor Class and Hit Points as an abstraction invented for game mechanics but now “roll to hurt” really brings the point home for me. Thank you for sharing this idea. Whether you came up with it or not this is the first time I heard of it.

  5. Joshua Macy says:

    As far as I know I coined the phrase for this post, though the concept is probably almost as old as arguments about AC….still I don’t feel like it’s in as wide circulation as I think it deserves since you still see people arguing AC makes no sense because armor should if anything make it easier to “hit” you.

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