Could you combine the effects of Shield Master (feat) and Protection (Fighting Style)?

Question

Could you combine these and forego your own possibility of hiding behind your shield for an AoE and instead shield a companion within 5ft?

This would be the relevant part of Shield Master

If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect.

Protection

When a creature you can see attacks a target other than you that is within 5 feet of you, you can use your reaction to impose disadvantage on the attack roll. You must be wielding a shield.

I'm guessing not but the question got asked at my table.

Answer 1

No.

Each of these abilities provide a separate reaction and neither provides a way to combine them.

Oath of the Crown provides a similar effect

If your player is interested in playing a style where they focus on defending others you may be interested in the Oath of the Crown Paladin from Sword Coast Adventure's Guide. At 7th level they gain Divine Allegiance which lets them use their reaction to take the damage for another creature giving a similar effect to this combination.

Answer 2

Not technically. Each power does just what is says and no more - shield master procs off a Dex saving throw you make while protection procs off an attack targeting an ally, two totally different triggers.

But of course you are welcome to rule that the combo works if it seems good for your own game. If that PC really wants to focus hard on the protecting others bit, you could have them give up another power or feat to "apply any of your shield abilities to an adjacent ally" or similar.

Answer 3

There is nothing in either ability which would allow you to combine them. They give you 2 entirely separate reaction options with very different benefits.

On the other hand, Shield Master is quite a weak feat, and Protection is quite a weak fighting style. So while there's nothing in the rules that says you can combine them, if someone at my table had taken both and wanted to combine them I'd probably work with them to make it happen.

It doesn't seem likely to cause any problems, either - it's not giving them a new ability, just allowing them to give an ally the benefit of an existing ability.

Answer 4

No, there is no scenario in which they would combine anyways.

If a spell or another effect requires you to make a saving throw, it does not have an attack roll and thus there is no attack roll for protection to impose disadvantage on.