Sneak attacks in Fate Core

Question

I know that Fate Core is a bit loose with letting you interpret the rules as they make sense in a narrative context, but I want to understand what's written regarding the use of stealth.

First, the stealth skill can be used to Create An Advantage (FC99):

You’ll mainly use Stealth to create aspects on yourself, setting yourself in an ideal position for an attack or ambush in a conflict. That way, you can be Well-Hidden when the guards pass by and take advantage of that, or Hard to Pin Down if you’re fighting in the dark.

But then in the section on active vs. passive opposition (FC131), it says in a sidebar (emphasis mine):

Sometimes you’re going to run into edge cases, where something inanimate seems like it should provide active opposition (like an automated gun) or an NPC can’t provide proactive resistance (like if they’re unaware of what the PC is doing). Follow your gut—use the type of opposition that fits the circumstances or makes the scene more interesting.

This is reiterated specifically in the section on the Attack action (FC140):

Most of the time, your target will actively oppose your attack. Passive opposition on an attack means you’ve caught your target unaware or otherwise unable to make a full effort to resist you, or the NPC isn’t important enough to bother with dice.

Does this mean that, for a stealthy character attacking another character who is unaware of their presence, they would be able to (1) use stealth to create an advantage, (putting a freely-invokable aspect on themselves), and also (2) when they attack on a subsequent turn, deny the opposition of the ability to roll dice? Under what circumstances would it make sense to give both bonuses, or to only give one or the other?

Answer 1

You have a few questions all rolled into one, so I'm going to tackle them one at a time.

Does this mean that, for a stealthy character attacking another character who is unaware of their presence, they would be able to (1) use stealth to create an advantage, (putting a freely-invokable aspect on themselves)

Whenever it's appropriate, you can make a skill roll to create an advantage. Of course, if it's a bright day outside and there's nothing to hide behind you're going to be facing a higher opposition.

and also (2) when they attack on a subsequent turn, deny the opposition of the ability to roll dice?

You quoted it yourself in your question, "Passive opposition on an attack means you’ve caught your target unaware" (citation). If they are not aware of you, they don't get a skill roll.

Under what circumstances would it make sense to give both bonuses, or to only give one or the other?

When you successfully create an advantage, you have the free invokes as long as the aspect is around. If you are Hidden in Shadows then show yourself, the aspect goes away ("A situation aspect is temporary, intended to last only for a single scene or until it no longer makes sense…" [citation]).

They can, however, be aware of you even if you are hidden. In a conflict where the opponent has seen you and then you disappear is aware of your presence, even if they can't see you. Them not knowing exactly where you are is covered in the invoke(s) of the Hidden in Shadows aspect. So in such a case you would only get the free invoke(s), not the passive opposition.

If you sneak up on them and then attack, with them never becoming aware of your presence, you'd get both. In a conflict, you could most likely have this happen during the first, maybe second, exchange. If you're not in a conflict scene, however, and you're trying to do an Assassin's Creed-style stealth takedown, that's an overcome action, not an attack. It can still benefit from the Hidden in Shadows aspect, though.

A conflict is defined "[a]s long as the characters involved have both the intent and the ability to harm one another, then you’re in a conflict scene", (citation). If they are unaware of you, they don't have the ability to harm you. Thus, not a conflict and not an attack (in my opinion).

Answer 2

This is one of those cases where it's all about gut instincts and common sense.

For example, being Well hidden could justify getting passive opposition (your target won't see you coming), but probably not getting a bonus on the attack that ensues (being hidden does nothing to improve your ability to throw a punch / shoot straight).

Rewrite it as Ready to pounce from the shadows and then, maybe you have a case to get both. You're implying that not only have you been hiding, you've also been preparing a nasty trick to play on your mark.

I, as a GM, would also set the difficulty to Create the second slightly higher than the first.