I wonder if I am missing something or failing to understand the rules. Please, can someone explain to me: When and why should someone use disarming and grappling in a melee fight? Or why not at every opportunity? It does not 'feel' like a consistent combat rule system. I am asking as DM, but I try to keep the players side in mind, too.
First of all, I ask on the assumption that both fighting options are generally available for NPCs and monsters alike (of course, it individually depends on intelligence and body).
Here's the disarming rule from the DMG (p271), which will be the main focus of my questions:
A creature can use a weapon attack to knock a weapon or another item from a target's grasp. The attacker makes an attack roll contested by the target's Str (Athletics) check or Dex (Acrobatics) check. If the attacker wins the contest, the attack causes no damage or other ill effect, but the defender drops the item. (...)
Note: As I read it, the attacker can try to disarm for each of his own weapon attacks, so a fighter on 5th level can do this twice per round, correct?
In some fights (well, in most fights) the adventurers choose their weapons by their effectivity; large weapons with a lot of potential damage or weapons with a damage type or magic that the opponent (in the following, this term refers to NPCs and monsters) is not immune/resistant against.
So, any (at least minimum intelligent) opponent enduring (or fearing) severe damage by such weapons should try to disarm the wielder of that weapon. If that is successful, the effective (!) challenge rating of this encounter may rise - all of a sudden: Think of a vampire that successfully disencumbered the adventurers of all their magic weapons. Or a flesh golem ... This strategy would give the opponents quite an advantage.
On the other hand, if I (as DM) start to disarm the characters regularly (or try to), they will pick up the idea pretty soon. Most opponents don't carry an arsenal and many don't have special acrobatic or athletic skills and, therefore, the disarming attempt is quite likely successful (and I strongly dismiss the idea of having to keep the inventory of each opponent up to date) . In the end, most opponents will be far more easily conquered if without appropriate weapons. So, in the end, the game balance would swing to the other side; the players will have the advantage, and because of that, I fear to integrate this disarming option into my games, although of course, players ask for this now and then.
Any attacker with a decent attack bonus can hope to disarm its opponent. (And in situations when damage immunity or resistance is important, it's well worth trying several times to disarm the fatal weapon.) If it succeeds the weapon should be kicked away (free action) so that the disarmed opponent can't take it up again with a free action in its turn without running to it (maybe it is better for the attacker to 'place' the weapon on his own tile (AKA 'step upon it'), in order to 'guard' the weapon? But otherwise kicking away may offer an attack of opportunity ...) Of course, the opponent might have more weapons on him, but in most cases those will be of lesser use / inflict lesser damage and so on.
I don't want to make disarming more difficult, but how can I prevent disarming to become the main strategy, in particular for the players? And I don't think they would have solely humanitarian reason for doing so.
As with grappling, its mechanic seems very similar to me in general, but the question is reversed: Why should someone grapple someone else? Some differences are:
- It requires a dice contest: Str(Athletics) vs. Str(Athletics) or Dex(Acrobatics) - that looks like the average chance of success is about the same as with disarming.
- Escaping the grapple requires an action (opposed to a free action to pick up or draw a new weapon) - that's a real disadvantage, but ...
- ... since being grappled doesn't prevent a creature to attack, this is really an advantage compared to being disarmed.
Unless one of the effects of having the opponent grappled (opponent has speed 0 and is dragable) is important to the attacker, grappling seems to be useless. Although I admit that the ability to drag the victim CAN be very important, grappling is not a requirement to shove an opponent over the edge of a cliff (PHB p198, 'Shoving a Creature', and DMG p272, 'Shove Aside'). Pushing an opponent to the ground (making it prone) doesn't require to grapple it neither (see again 'Shoving a Creature').
Grappling would make more sense if fighting with weapons (except small weapons like daggers, knuckles) while being grappled would gain disadvantage at least, but that I cannot find in the rules.
Here the circle closes: I would think, that an disarmed (or unarmed) opponent faces an armed attacker, it will try to grapple the attacker in order to get into a close-combat situation (wrestling, fist fighting, ...) where weapons can't help much - or to flee completely.