D&D 5E Can a character tell when they are in danger of drawing an Opportunity Attack, notably in regards to Sentinel & Polearm Master?

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Can a character tell when they are in danger of drawing an Opportunity Attack, notably in regards to Sentinel & Polearm Master?

Since this edition is more rulings than rules I'm wondering how folks are handling the feats and possibly other abilities that grant AO's beyond the normal 'moving away from combat' ones.

In my opinion a character should be able to tell, since skill at the level to grant such OAs should be apparent to rival combatants.

• Your foe you seems exceptionally skilled with her polearm, leaving no gaps, you don't see how you could close in without letting her strike at you.
• Your are barely able to keep your foe's weapon away, you suspect if you fail to focus solely on her, she'll find a gap in your defenses and strike.
• Just as you begin to withdraw, even with careful and guarded motions, you realize from her stance and weapon flourishes that she will get a chance to strike you if you back away.

Dissenting opinion...

Cannyjiggit said:

I would rule no until they have seen it happen just like I wouldn't tell the players if their opponent had such a feat. Even once it has happened, I wouldn't be explaining why or how to players until after the session but would let them draw their own conclusions. I do prefer campaigns where players will try to accurately roleplay their characters knowledge and not know everything just because its open information in the books (this includes knowledge of spells and how to frustrate them such as with Witchbolt unless its a spell available to them)

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I'm currently leaning towards no, but I suppose I'll make up my mind when it comes up.

I voted No, with the caveat that enemies have the ability to learn from observation and pain. The more intelligent those enemies, the faster they learn and adapt.

Great fighters aren't just good at making an attack, they are very good at making that attack without telegraphing it, and making it work despite everything the enemy does to defend. Like an exceptional boxer with an amazing jab, the polearm master isn't doing anything very complicated, they are just doing it with a frightening level of speed, power and expertise. I agree that an opponent will learn to modify tactics to avoid the attack, but they are almost certainly going to get caught with it a few times before organizing an intelligent counter-strategy.

Besides, how long do you think it would take someone, after taking a lightning fast halberd jab to the belly, to realize the severity of the threat, accurately judge the range, stay out of the danger area, and advise their friends on the best strategy, while engaged in pitched combat? 6 seconds? 12? 18? 24? Those rounds tick by pretty quickly.

If the character is risking an opportunity attack, I would ask, "Are you using your action to Disengage?" The player can say yes or no.

Conceivably, I could ask the same question if an opportunity attack were not riding on it, but it is of much lower interest for me to do so, and most of the time, I do not.

I voted "no", but I would prefer that there was an option for "sometimes".

Smart players will know when a monster has threatening reach or some similar ability which provokes unexpected opportunity attacks. They might find out the hard way the first few times. As DM, I'm not going to tell 'em. So, no, I'm definitely not going to give them the flava text that they suspect a monster will get a free shot if they try to disengage. But they'll work it out eventually... and then they'll apply that knowledge to future PCs, whether or not those PCs have any experience with that particular monster. If they take the time to do a Monster Knowledge check as a Bonus Action, I may give them a strong hint about the possibility of Threatening Reach (or Polearm Mastery, or whatever). That's probably a DC 15 or 20 Monster Knowledge check in one of my games. They'll also get a summary of other information about the creature, of course. e.g. "You reckon it's a bone golem! These legendary creatures are created by evil necromancers. They're highly resistant to magic, and outright immune to most mind-affecting spells. You really don't want to get close to their 4 sword-wielding arms, and you suspect that it'll be very difficult to disengage once you're in melee. However, you also recall that they have a weakness to some types of bone-shattering energies..."

Monsters should be about the same. Stupid monsters won't care. They will provoke the Opportunity Attack if they feel the need to move, and will do so repeatedly under some circumstances. That's good, because it makes the PC feel like they're getting value from their feat. Smarter monsters might fall for it once, then make an informed decision thereafter. REALLY smart monsters (genius+ foes; pit fiends, liches, dragons, etc) might be so long-lived and experienced that they automatically recognize the tell-tale signs of Polearm Mastery (etc) even before they provoke the first attack.

If a player knows enough that trolls are killed by fire, and liches have phylacteries, and undead are immune to sleep, and black dragons have an acid breath (even before any of these abilities are actually visible in combat)... then certain monsters will know that the adventurer with a halberd is almost certainly going to have the Polearm Mastery feat. Those tricksy, tricksy adventurers... we hates them all...

Definitely.
An experienced combatant depends on reading the opponent.

And that way makes for more interesting choices, not just a 'gotcha'.

IMO no the character shouldn't know an OA is provoked by movement that typically doesn't provoke unless they already saw such creature doing so. Just like monsters don't know characters abilities until they seen it happening i.e Protection Fighting Style.

I'd let them know in this case. I'd treat it as "everyone knows that polearms are used to strike before the foe gets too close". It's ok if it happens only with the feat rather than being an automatic property of the weapon, it just means it generally requires a specific training to "unlock" that property.

On a tangent, I really wish that WotC didn't build any character material on top of the OA rules. There is just to much risk of opening a can of worms. OA rules originally served the sole purpose of giving a penalty for fleeing from combat (and later for trying to get past a defensive line with impunity). Let OA stay that way, and it will avoid a lot of troubles.

Li Shenron said:

On a tangent, I really wish that WotC didn't build any character material on top of the OA rules. There is just to much risk of opening a can of worms. OA rules originally served the sole purpose of giving a penalty for fleeing from combat (and later for trying to get past a defensive line with impunity). Let OA stay that way, and it will avoid a lot of troubles.

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Agree. IIRC there used to be a big bonus for hitting fools who tried to flee a melee.

Can a person that is trained to fight understand that they could be attacked by moving around someone who looks to be a trained fighter? Yes.

Is it always cut and dry? Oh heck no.