Monk's Martial Arts and Polearm Master

Question

I have a problem with an interpretation of the outcome of a monk with the Polearm Master feat, wielding a quarterstaff.

1. You can take the Attack action and attack with a quarterstaff using Dex instead of Str and dealing 1d4 (monk), 1d6 (normal) or 1d8 (versatile) damage.
2. Then you can use a Bonus action and make an unarmed strike using Dex instead of Str, dealing 1d4 (monk) damage.
3. Or you can use a Bonus action from from Polearm Master and make a weapon attack using Dex instead of Str, dealing 1d4 (polearm master) or 1d4 (monk) damage.

Note: Monk's Martial Art damage goes higher with levels up to 1d10.

Am I right with my interpretation? Especially the part of using a monk's damage die instead of the Polearm Master die. I don't know which "die replacement" is more specific.

Answer 1

You make your attack with a quarterstaff using Str or Dex. You then deal damage either as per monk level or 1d6 for staff or 1d8 for versatile.

You then choose whether you make a monk bonus action attack or polearm bonus action attack, and get the replacement damage die that comes with the bonus action you chose.

As you gain levels only the monk attack damage would go up; your polearm bonus attack would remain at 1d4. You cannot apply your monk level bonus damage to the polearm bonus attack, but you would gain the bonuses of a magical weapon in that regard, both on attack and damage.

Sidenote: Some DMs may rule that using a quarterstaff in two-handed (versatile) mode doesn't count as a monk weapon, as two-handed weapons cannot be used for monk weapons. Such a ruling would remove the option to make an unarmed strike as a bonus action, but you would retain your polearm bonus strike option. For RAW the option remains.

Answer 2

Martial Arts
• You can roll a d4 in place of the normal damage of your unarmed strike or monk weapon. This die changes as you gain monk levels, as shown in the Martial Arts column of the Monk table.

Polearm Master This attack uses the same ability modifier as the primary attack. The weapon’s damage die for this attack is a d4, and it deals bludgeoning damage.

Quarterstaff is a monk weapon.
Weapon damage is d4 (in this case)
If you use the Polearm Master Bonus Action attack with a quarterstaff, you are still using a monk weapon.
Martial Arts lets you replace a weapon's damage die with your Martial Arts damage.
So yes, you could improve the BA attack damage.

Notice Martial Arts does not mention "when you take an attack action." It doesn't seem to have situational limit, only that it should be unarmed or monk weapon.

Answer 3

Polearm Master can use the monk damage die.

The PHB states that the monk damage die can replace the damage die of an unarmed strike or a monk weapon - and with polearm master you are still using a monk weapon to make the bonus attack.

It doesn't increase your damage in any shape or form.

By the time your damage die increases you can either do 1d6+dex unarmed strike or 1d6+dex bonus attack with polearm master. It doesn't break the mechanics in any way as monks can use 2 handed weapons which don't have the heavy property it's only flavour.

The PHB dosn't state anywhere that you need a free hand to make an unarmed strike (kick, headbutt, knee, bodyslam etc.) Furthermore, once you get to level 12 all your attacks with a quarter staff (1 or 2 handed) or unarmed strike have the same damage die.