Is Arms Law Broken?

The only things that RM really has that no other system comes close to is Arms Law with its descriptive criticals and black humour. Everything else is pretty run of the mill, the skills are the same skills found in just about every rpg, stats are stats. The spells are for the most part just reworkings of standard fantasy fare. The only stand out feature is the combat system.

But Arms Law doesn’t work and really has never really worked. How many times have you had someone stood behind a wall get hit in the leg? Why can you never shoot a dragon in the wing? Ignoring Size rules for a second why does a glancing blow from  the jaws of a Tyrannosaurus Rex do the same damage as a glancing  blow from a mouse? The promise or the premise was that to hot and damage were combined so a good hit did more damage than a hit that barely succeeded but you can roll a 1000+ with an open ended roll followed by a poor critical and do no more damage than a mediocre roll followed by a decent critical. In fact a roll totalling 150 is identical to a roll totalling 1000+ unless you start adding in optional or house rules. The promise of the better the attack roll the greater the damage doesn’t really work.

The criticals are supposed to add flavour and a gritty realism to combat but if the text refers to a body part that is impossible to hit, due to cover or doesn’t exist it just makes more work for the GM to translate the critical text into something viable.

I don’t think one can really call 10th level ‘high level’ in a game where there is an explicit range of 1st to 50th but a combat centric character can easily have an OB up around the +150 by 10th to 15th level with 20-30 ranks, plus a stat bonus, level bonus and superior weapon. So as long as you can roll more than the targets DB you will max out the table almost every single time.

Then there are the criticals against super large creatures. The whole idea of weapon specific damage does out the window at that point and everything from martial arts to crossbows do exactly the same damage effects.

Then we get to tiny through to huge attacks and rank one to four in martial arts. The idea of damage caps work for maximum damage but not for minimums, mice can out bite dragons.

One of the things that people asked for was attack tables that went over the 150 cap. The 175 cap really did nothing to solve the problem that caused the complaint in the first place. If anything the fact that RMU kicks off play at 3rd level makes the problem worse as characters will have table busting OBs sooner. The RMU solution is DB inflation with actively-passive-running-footworky-shieldy-dodgy-parryingmajiggy.

Arms Law does not work but we put up with it like an old dog that smells like a damp rug and farts constantly, because we love it and we could not imagine living without it.

The size rules attempted to  solve the problem of an identical final attack roll from a mouse and a dragon bite doing the same damage, while removing the damage caps. This is the only thing that the size rules did well. If we use the compound tables with a bulk of the most common sizes all one table then you get a sticking plaster that functions in this particular instance.

The flaw is in the core Arms Law mechanic.

Roll the dice + skill + mods – DB -> look up the result, roll critical (if any).

This has never changed and is the core problem.

I am not suggesting this as a fully thought out solution, I am writing it on the hoof but…

If you took the bit that says +mods and moved it so that you get…

Roll the dice + skill – DB -> look up result, roll the critical (if any) + mods.

I have cheated a bit there as things like cover and magic and being stunned would effect DB but that is not what I want to focus on.

By adjusting the critical for size, something like +/-10 for each size step difference may work. Rearrange the results so the lowest critical results are feet and shins and the highest are shoulders, neck and head and you have a result that mice would be really pushed to ever bite a giant above the knee and if a dragon takes a swipe at you it is unlikely to hit your foot.

One of the breaking 150 options was to add +1 to the critical roll for every 10 over 150. This would work perfectly well. Now rolling up in the multiple hundreds would make a difference. You would not be rolling 500+ and then getting a critical of 01 and no bonus.

You can scrap criticals A to E and just have 100 possible critical results on a linear scale, maybe 2% or 5% apart. Now all criticals can be open ended!

Size need not be the only critical mod. If DB is about hit or miss, that is where parry belongs. Shields on the other hand can be used to turn a blow away, thus adding to DB, or by putting the shield in the way thus protecting the person so that can be used as a critical mod.

Cover may not add to your DB but it could protect against criticals from 01-30 for a low wall or from 31-80 if you are stood behind a cart with your head and feet visible but the rest of your middle section hidden.

Weapons could come with a critical mod. You are highly unlikely to stab someone in the foot with a dagger as you would have to really reach down intentionally to do so. A battle axe though is probably more likely to do a wound to the lower half of the body, (I stand to be corrected there as I am just spieling off ideas as they come to me). I can imagine parrying an axe coming down at my head or shoulders but the momentum and follow though taking the axe head down to the legs or even feet. As long as the size mods out weighed the weapon adjustments you are still most likely to get stabbed by a hobbit in your leg or abdomen, not the neck or shoulder.

All of a sudden you don’t need the size based multiples and reading up or down a critical tables in multiples of +/-10 is much much easier to do on the fly.

We no longer need this forced size multiples such as charging adding +1 size, now that becomes a critical mod. You even get to finesse things by making charging a penalty to hit, after all you are running around, but a bonus to the critical.

You do not even need the attack table any more. The attack roll becomes a 101+ skill check. You can combine the damage that would have been on the table into the critical descriptions so the skill roll is little more than a pass/fail/fumble roll.

If you combine armour references into the criticals e.g. If foe has a helm then +12 hits, otherwise foe is stunned 3 rounds +22hits. You now can roll out location specific armour and armour by the piece. Imagine an electricity critical  ‘Strike to the upper arm, if foe has metal armour then it is fused into a single piece -20 to all actions using that arm +20 hits, stunned 2 rounds. If organic armour then armour is destroyed +10 hits else, +15hits and burning 1 hit/rnd.’

We can add in breakage so all attacks are two d100 rolls either attack/fumble, attack/breakage check or attack/critical. That is nice and consistent with every action being two rolls ALWAYS.

Another alternative is that you have a traditional attack table of sorts but scrap criticals A-E. You now rename the columns Legs, Arms, Abdomen, Torso, Neck/Head. This makes it relatively easy to do called shots, you take a penalty to hit but choose the column for the critical. Weapons tables skew the columns to match the sort of weapon. So knives and daggers that are unlikely to hit something out of arms reach, like the feet do more arm, abs and torso criticals. Cover exclude unreachable criticals and position shifts the column left or right so attacking from above is more likely to hit the head than the feet. In this system you could have a single page of additional  Krush, Puncture and Slash Criticals but with columns for Wing, Tail, Tentacle and Fin. If a beast doesn’t have legs then the GM can substitute the tail column, if there are no arms then you attack the fins. Another creature may be all tentacles, head, body tail.

Arms Law was probably conceived on a wet Wednesday afternoon are a particularly dissatisfying D&D combat. Since that time it has remained basically unchanged for going on 40 years and not one of its shortcomings have ever been addressed.

The ideal solution may well be a combination of all of the above or things I have not even dreamt of but the fiddling around the edges of RMU’s Arms Law is not the right solution and solves nothing.


Extending the maximum result to 175 compared to 150 does nothing especially if people walking around with a +285OB. The 175 cap is a drop in the ocean. The most powerful PC I ever had had an OB of +193. It was extremely unusual for me not to do an E critical on almost every round. I don’t thinking going to 175 would have changed that.

To round it off, I think Arms Law is the heart of Rolemaster and unless it is looked at really critically and made fit for purpose then all the tweaks in the world will just make it slower and more cumbersome and not solve the real problems.


7 thoughts on “Is Arms Law Broken?”

  1. Arms Law, at least the model, does work fairly well if you actually take on the elephant in the room: how damage is determined. I’ve gotten it to work quite well for firearms, although my crit tables are based on hit location. They still use the A-E model, which is useful when dealing with weapons that have a determined damage cap.

    I also added more To-Hit penalties, since the AL model has always been somewhat weak in that area (which I think comes down to a lack of damage formula and that pesky ‘flurry of blows’ model which leaves attacks lacking vital specificity). Your first shot might top the chart, but after that things decrease rapidly.

    Getting rid of attack tables and going over to solely crits really solves nothing, and if anything increases the issue of no damage formula. It also doesn’t address the fact that some weapons simply won’t be capable of doing what might be called E-class damage.

    1. Firstly, this is in some regards part off the problem. AL works ‘mostly’ and you can house rule around some of its shortcomings. Both HARP and the RMC Combat Companion have weapon specific criticals so a Dagger, Dirk or Sai will use one set of criticals with the full A-E range. Broadswords use different criticals. Bolts, Arrows and Bullets would all have completely independent critical tables. Long, short and composite bows would share a table. So it is not one weapon one table, which would lead to massive page bloat.
      So in one attempt to solve some of AL’s problems changing the criticals was seen as the answer but keeping the full A-E range.
      You suggest that some weapons are not capable of E scale damage which is another way of addressing the same thing.
      I was suggesting that AL needs a more fundamental overhaul party because people like you have had to house rule and rewrite to make it work.
      I also said that I was not proposing a solution, just postulating different ways that could be used to start a discussion.

  2. Your rant asks some really profound questions. I agree with some of your criticisms, but I have to disagree with others.

    Why does a glancing blow from a Tyrannosaurus do the same as a glancing blow from a mouse? It doesn’t anymore, with RMU’s new size rules. So that problem has been solved. Also solved in RMU is the problem of damage caps, due again to the new size rules. So I think you need to distinguish which version of Arms Law you are talking about. The new RMU version solves some of the things that were broken in previous editions.

    I also don’t really see a problem with the possibility of having a high attack roll and a low critical, or vice versa. Even a well-aimed spear thrust can fail to hit any vital organs, while a badly aimed thrust can get lucky and pierce the liver. I very much dislike the idea of adding bonuses to the critical roll for attack rolls that break 175: that in my experience makes death a lot more likely… and I think Rolemaster combat is already deadly enough.

    Your point about the criticals is well taken, but remember that RMU does make a clear advance over previous editions insofar as it gives RM a consistent, location-specific critical system for the first time. Rolls of 46-55 are always an arm on all critical charts; 76-80 is always the chest. This makes procedures for called shots much easier and more common sensical, even if you don’t want to use the default rules for that. For example, if you really wanted to simulate the effects of cover, you could either entirely negate criticals that hit a body part that would be impossible to hit, or allow cover to give critical reductions, or combine the two; perhaps soft cover could give a 1 or 2 severity reduction, and hard cover could negate criticals entirely. Or you could change the critical result to the next number on the chart that would strike a body part that is vulnerable. There are lots of possibilities here, and the new RMU makes all those possible; they were not quite so possible in earlier editions (at the very least they were a lot harder to make work).

    I agree with your criticisms of RMU’s passive DB bonuses, as well as the problem of DB inflation. I would prefer to see those passives gone. But let’s not forget that RMU has raised the number needed to deliver criticals for almost all armors, so that does at least mitigate the high OB problem. And while raising the attack charts to 175 won’t solve the issue completely, it is I think a step in the right direction. High OBs can also be countered by parrying, which is still very effective.

    I’m not opposed to making charging a crit severity mod rather than a full size mod. A full size mod is in the end just a crit mod + a hits mod, but I think it shouldn’t be both. I think it should be one or the other, since making it both confuses the charging mod with the size mod.

    If every missed attack roll resulted in a fumble or breakage check, then fumbles and breakage would happen way too often. I prefer just to roll breakage whenever I roll a fumble (e.g. when I roll 01-04 on a percentile attack roll for my Broadsword.

    Perhaps the most interesting thing I took from your ideas was the idea of cover modifying criticals. I think the idea of soft cover providing only a crit severity mod while hard cover negates crits is really fascinating; I might try it in our next playtest!

    1. I really don’t think the new “hit location” crits do much for targeted attacks, frankly. It would have been fairly simple to do something like reversing the attack roll to determine hit location. Then you’d know where the attack hit and could resolve it on both the proper AT column AND location-specific crit table. And if you’re using a system like this it also works with cover…if the hit is in a location that’s protected by cover the roll is either modified or negated depending on the type of cover.

      I do agree we don’t need checks for fumbles or breakage with zero damage attacks, though. In a firearms system that’s just a miss, and would likely be the same for RM missile attacks. Melee could mean whatever you want with the ‘flurry of blows’ thing.

  3. I didn’t think I was ranting but it is entirely possible. 🙂

    It is my understanding with RMC that if obviously if you roll in the fumble range than you roll a fumble. If you do not fumble but do not do any hits then you roll a breakage roll. If you do hits but no critcal then that is the end of your attack and if you do a crit then you roll it.
    I am only thinking that if the ‘hits only’ results became the lowest results in the critical table then you lose that whole ‘hits only’ strata of results.
    To all intents and purposes a plus/minus to OB has the same effect as the multipliers in the glancing blow scenario if you are looking at purely #hits and no crit results. If you get rid of those and go to a small creature biting upwards and a large creature biting downwards then you significantly different results. The mouse would be biting your toes and the T. Rex your head, shoulder, arms and torso.

    As I said, I am not putting forward a fully thought out alternative. It is just that AL as it stands in all versions does not cope with non-standard, to people stood there knocking lumps out of each other, situations.

    We both noticed that the standard damage is too low but my increasing the base damage when you apply the size multipliers to the damage the upper ranges get really massive. For example, a bull charging a small target is likely to do something like 150hits which could kill outright with or without a critical. (I don’t have AL on me right now so that is a figure pulled form the air.)

    Another consequence of the size rules is that looking for a way to gain size mods has become almost a way of gaming the system. I don’t want to turn this into an anti size rules post but they do add a lot of book keeping even with the alternative composite tables. A targets DB changes with the relative size differential, effectively many times during a combat round if you have a fight against orcs, goblins, a couple of ogres and a hill giant against a couple of hobbits, a dwarf, human and a elf.

    Armour by the piece and called shots are a point of weakness in AL. If you do not know the location of the hit until you roll the critical how do you know which armour type to apply the attack roll against? In a fixed always roll 2d100 system then, the second roll could be applied to the fumble, breakage or critical as required. It is no extra work.

    The RMU critical tables are arranged with a repeating pattern of head, chest, groin, arm, leg. If they were arranged so all the legs were at the bottom and the heads at the top then critical mods could reflect relative size.

    Attack tables could also feature a little person shaped icon showing the percentage ranges for each body location so as soon as what is the second roll is made the location is known. If you did the rolls the other way around so one rolled ‘targeting’ first and the attack roll second then a piecemeal armour system would work. You roll targetting getting say an 81. You now that will be a head shot, the target has a full helm so that is AT 10. Roll to hit, and you get an C crit so the result is “Point passes through cheek, foe spits up blood. Foe cannot speak clearly until bleeding is stopped. + 8 Hits, 4B, -25” . If the attack vs AT10 had missed then the 81 would have been the breakage check or on a fumbled it would have been the fumble roll.

    I do not know the answers but I am conscious that there are too many exceptions where things do not work.

  4. @IntoThatDarkness: ‘Arms Law, at least the model, does work fairly well if you actually take on the elephant in the room: how damage is determined.’

    Yes, agreed. The current tables tend to be a bit too similar; I’d like to see a bit more variation in the damage the weapons do against specific armor types (e.g. slashing vs no armor, a warhammer vs. chain armor, et.).

    @Peter: ‘It is my understanding with RMC that if obviously if you roll in the fumble range than you roll a fumble. If you do not fumble but do not do any hits then you roll a breakage roll. If you do hits but no critcal then that is the end of your attack and if you do a crit then you roll it.’

    I don’t know how RMC works, and I honestly can’t remember the RM2 rules for breakage, as we never used them. But that sounds like too many rolls to me. I prefer the RMU rules: the basic one is that if you roll a 33 or 66 on an attack, you do a breakage check. That is fine. We have a house rule though that makes it even simpler: whenever you fumble, you roll breakage too. It makes fumbles a little worse, but RMU has allowed characters to reduce the fumble range as you move up in skill in a weapon, so it balances out reasonably well. I find it easier to remember to roll breakage when I fumble than to roll it when I roll a 33 or 66.

    The idea of low crits being leg crits is interesting, but I’m not sure it will always make sense. What if a Tyrannosaurus rolls a low crit? Can he still bite your foot?

    I like the way the current RMU size rules give multipliers for larger attacks (which RM2 actually did do for some creatures, though not in a systematic way). If a bull charges a Koala and hits, even a glancing blow, I have no problems with the bull killing the Koala outright due to concussion hit damage. That seems entirely appropriate to me.

    @Peter: ‘A targets DB changes with the relative size differential, effectively many times during a combat round if you have a fight against orcs, goblins, a couple of ogres and a hill giant against a couple of hobbits, a dwarf, human and a elf.’

    I’m not sure DBs change at all anymore (if they ever did; was that in Beta1?). I had suggested giving smaller targets a DB bonus, but I don’t think that is in the rules. I am pretty sure Halflings do not get a bonus, nor do I think there are any relative bonuses.

    @Peter and IntoThatDarkness: ‘Armour by the piece and called shots are a point of weakness in AL. If you do not know the location of the hit until you roll the critical how do you know which armour type to apply the attack roll against?’

    I agree the armor by the piece rules needed some bug fixes, but there is an easy workaround, and both you and IntoThatDarkness are getting at it. The solution is simply to determine hit location first, then roll the attack. The hit location also does double duty as the critical roll, so you don’t have any more rolls than you normally would for an attack that crits. So, you can fix any problems with the system by simply rolling critical first; we’ve been doing this in our playtest for a while now and it works. There is an additional upside in that it now allows you to have all armor types (1-10) at all body parts; you don’t just have light, medium, and heavy greaves; you can have chain (AT 8) on one greave, plate scales (AT 7) on another and full plate (AT 10) as your helmet. JessicaEwers has worked out a whole system for this, with additional mods for each armor type (e.g. lead-lined silk to give a bonus against fire attacks).

    Or of course you could do what IntoThatDarkness suggests, and make the location the reverse of the percentile attack roll. Either way, the new size rules work quite well with the armor by the piece rules once you make this simple change.

    So basically, I think both of you are arguing in favour of the changes Jessica and I also support; and once they’re made, the location-specific hit rules mesh quite well with the new armor and size rules.

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