How do the Sanctuary spell and the Sentinel feat interact?

Question

The description of the Sanctuary spell (PHB p 272) says:

You ward a creature within range against attack. Until the spell ends, any creature who targets the warded creature with an attack or harmful spell must first make a Wisdom saving throw. On a failed save, the creature must choose a new target or lose the attack or spell.

The description of the Sentinel feat (PHB p 169) says:

When a creature within 5 feet of you makes an attack against a creature other than you...you can use your reaction to make a melee weapon attack against the attacking creature.

If a character with the Sentinel feat is also warded by Sanctuary, and an attacker fails the Wisdom saving throw and attacks a different target within 5 feet of the character, will this still trigger the melee attack reaction?

Answer 1

Yes, the attack being caused by Sanctuary will not prevent it from triggering Sentinel. You've already quoted the important rule:

When a creature within 5 feet of you makes an attack against a creature other than you (and that target doesn't have this feat) you can use your reaction to make a melee weapon attack against the attacking creature.

There's no conditions placed on this. If a creature within 5 feet of you makes an attack against a creature other than you, you get your reaction to hit them. It doesn't matter what kind of attack, it doesn't matter what caused the attack. Any attack triggers Sentinel.

Answer 2

Absolutely.

The trigger for Sentinel is "When a creature within 5 feet of you makes an attack against a creature other than you". An attack is rolling a d20 to overcome AC - if someone does that then you can thump them.

The reason for making the attack is irrelevant; its the fact of it that matters. Sentinel does not care if the attack was made as a result of Sanctuary or because of what that guy said about our Sharon.