An initial stealthy/surprise attack with subsequent adventurers entering combat afterwards?

Question

A group wants to maximise the potential for surprise attacks using their stealthy members. They don't want their less stealthy members to blow a surprise attack.

A party of four; two stealthy, two not. The two stealthy members travel in to a room (~30 feet or so) and leave the two non-stealthy members behind the door/in the previous room (hidden).

The two stealthy members throw to surprise some monsters in the room. After the first round of combat (which may include the monsters being surprised and not acting), the second round of combat starts and the two non-stealthy adventurers enter the room and enter combat. The two non-stealthy members did not want to try and surprise the monsters, they know they're too noisy, so they wait outside the room and out of sight and still.

Worked example

The party is two rogues with +7 Dexterity (stealth) and two dwarfs with -5 Dexterity (stealth). The dwarfs don't want to blow the potential to surprise the two orks with passive Wisdom (Perception) 15, they want to stay out of the room containing the two orks.

The two rogues throw stealth checks of >15 and the orks are surprised. The first round of combat occurs (containing only the two rogues and the two orks), the orks are surprised and cannot attack. After the first round of combat, the orks are not surprised. The two dwarfs now run in to combat, with initiative being throw for this 6 creature group.

Question

Is this permissible under the rules? Would DMs out there ask for/permit this selective throwing for surprise and (after that) for the rear guard to enter combat after the first round of combat (in which the monsters were surprised)?

Note

This is related but disimilar from How to determine surprise when only part of a side is stealthy?. I am asking about the temporary splitting of a party to allow a stealth member only surprise attack followed by non-stealthy members entering room and entering combat.

Answer 1

Basic

I'm going to address the general case rather than the highly specific example in the question. General guidance will be more useful to other readers with a similar question.

That said, let's start with the rules text...

If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn’t notice a threat is surprised at the start of the counter.

By definition, the whole group of player characters are trying to surprise the monsters, or none of them are. The less-capable ones can remain stationary and further away to facilitate that surprise, but they're still involved and still need to roll. The surprised/not surprised status is determined before initiative is rolled.

The reality is that the entire party is trying to be stealthy - some are just trying to do it while moving. The thunky rear guard group still needs to make Dexterity (Stealth) checks, but there are some modifiers that should be applied - advantage and disadvantage.

• The complete lack of motion could grant the folks hanging behind advantage on their checks - in all likelihood simply washing with the disadvantage from the armor they're probably wearing.
• The distance and obstructions could impose disadvantage on the passive Perception of the enemies, but only against the rear guard and only if they're far enough back that the distance is a hindrance to the targets. If they're just outside the room, no disadvantage should apply. If they're down the hall or around a corner, then it just might.

In effect, the advance team rolls Stealth with a DC of the targets' Passive Perception. The rear guard rolls Stealth with advantage against a DC equal to the targets' Passive Perception - 5.

From there, simply follow the normal rules for surprise. What they can do when the round begins can vary - maybe they don't have enough movement to get close enough to do anything, maybe they're forced to dash, maybe they have to use ranged attacks. There is no "Surprise Round" in 5E, as in previous editions.

Advanced

Because the rear guard is also ignorant of when the advance team actually strikes, it may be desirable (or at least somewhat more realistic) to consider them as three "sides" in the engagement, despite the fact that two are naturally allied.

Compare the rear guard's Passive Perception (you may consider giving them +5 for advantage because they know something is coming, just not exactly when) to the advance team's Stealth rolls, too, then follow the normal rules for surprise. This makes it possible for the rear guard to be surprised during the first round, making them a bit slow to engage because they have to wait for the sounds of conflict to know when to move in.

Alternatively, another method to reflect the rear guard's imperfect information would be to impose disadvantage on their Initiative checks. This could be interpreted or explained as them waiting until they're absolutely certain they heard the fight begin before moving in.

Advantage & Disadvantage

Advantage and disadvantage are among the most powerful tools at the DMs disposal for rewarding player thoughtfulness. They exist as a quick way to grant a benefit or drawback if the situation is good for a given participant. It has an almost minimal impact on speed of play, but can make players feel like their non-mechanical ideas have impact. What the exact advantage is doesn't matter. What the exact disadvantage is doesn't matter. If they have a big enough one to matter, apply it.

Answer 2

A DM does not allow (or forbid) players decisions

The two stealthy members throw for surprise attack on some monsters in the room. After any surprise attack round, combat starts proper and the two non-stealthy adventurers enter the room and enter combat.

Would DMs allow this?

Two party members decided to wait in the room. Two other party members are going to scout ahead, sneak into the next room and (probably) start a fight. If the fight starts, two previous members are going to join it. There is nothing wrong with this plan. If your DM says "no, you can't do this, because I don't allow it" it is clearly a bad DMing. But they can say, for example, "no, you can't join your friends in the fight, because you don't know they are fighting now".

DM resolves players actions

Typical tabletop role-playing game steps are:

1. The DM presents a situation
2. The players decide how the character acts
3. The DM determines the outcome and describes the results, creating a new situation

The real queston is — if you do that, what will happen? Will the monsters be surprised? What do they do? How fast will the rest of the party join the fight? The answer heavily depends on the situation and you current DM rulings.

In the April podcast Jeremy Crawford said that Stealth resolving are almost completely up to the DM in 5e. DMs are encouraged to use common sense first — for instance, if you are having a fight, it is obvious that creatures in the next room have heard you and are aware of the threat. They will probably join their mates, prepare an ambush, or run away, depending on their goals.

Anyways, the generic answer will be "it is up to the DM". Exploring an unknown dungeon, a party can not be sure things will go according to plan. The situation can always go unpredictable way. What if there are no monsters in the next room? What if there is a trap, that silently teleport your scouts somewhere? What if a vile creature stalks you, and attacks when you split the party? In the end of the day, it is the DM who decides what will happen exactly.

So what might happen?

The party are moving through a dungeon. From room 1 the party can hear some movement in a connected room 2. The two non-stealthy members back up against the wall next to the door to room 2 (in room 1), ready to run in when the combat starts. The stealthy members creep through the doorway between room 1 and room 2 and attempt a surprise attack on the monsters in room 2.

The main question is — will the monsters be surprised? Probably they won't. You can hear them, so they probably can hear you. Since two non-stealthy weren't hiding, they were already noticed:

Player's Handbook:
If neither side tries to be stealthy, they automatically notice each other.

But your party actually has two stealthy characters, who were trying to hide. That was covered in the How to determine surprise when only part of a side is stealthy? question.

Now, the second part of the question:

After the surprise attack when normal combat has started, the non-stealthy members charge in and are ready to fight in the first stage of normal combat. The non-stealthy have made no rolls for surprise attack.

Is is not clear unfortunately, because in 5e there is no special "surprise attack" as the opposide to "normal combat". There is no surprise round in 5e, instead a creature can be surprised or can be not surprised, that's all. Aside from surprised ones, all other creatures — PCs and NPCs, stealthy and non-stealthy — act normally. So technically the non-stealthy members can charge starting from the first round of the combat.

Answer 3

This is totally within the rules, and there are multiple valid ways to do it.

It's your call as a DM whether characters outside the room can be perceived by sight or sound. From the DMG:

Indoors, whether the sides can see one another usually depends on the configuration of rooms and passageways. Vision might also be limited by light sources. [...] Creatures can be more likely to hear one another before they see anything.

It sounds like your basic call is that the party is safe where they are, and that people who stay in this place remain safe if they stay there, even if some commotion happens in the next room. Assuming the distance and room configuration makes sense, that's a perfectly reasonable call.

If there's a chance that they could be seen through an open doorway or heard if they sneeze or whatever, you might follow the suggestions in other answers about giving them advantage and/or the monsters disadvantage. If you don't think there's a chance, just have them automatically succeed.

Your choice was to treat this as two separate combats — one very short one between the sneakers followed immediately by another one including the rest of the party. I think that's fine — the rules are light on guidance here. The "Combat Step-By-Step" says rounds continue "until fighting stops", so I guess a really pedantic rules-as-written interpretation would discourage this, but in practice you as the DM decide when to start and end initiative order, and I don't think there's anything wrong with what you did.

Another option would be to treat the groups as three sides. The combat rules described on page 189 in the PH say that "a typical combat encounter is a clash between two sides" and proceeds to explain the rules for that situation; I don't think there's anything spelling out how more sides works and we're just expected to use common sense. Here, give Side 1A (the sneakers) the opportunity to sneak into the room and possibly gain surprise, and tell Side 1B that they need to skip at least the first round in order for this to work. In this case, I'd have them roll initiative when they want to join in, following How to handle initiative when a new force joins a combat in progress.

Or, you could treat the attempt-to-surprise as a mini non-combat-encounter all on its own. This would be most appropriate if the environment is complicated, with a lot of opportunity to move around and get into different positions before everything starts. And, in particular, I'd do this if it's going to take the staying-behind characters a round to run into the fray anyway.

For this approach, have everyone roll initiative _or just pick the order they go in. Tell everyone that you're going to have separate initiatives for this operation and any possible battle. (Or just simplify and let everyone keep their rolls; I think it better represents the chaos of surprise to re-roll, but you don't want to surprise your players with this!)

On their turns, have your players describe their characters' movements, and have them make Stealth checks when close enough to need them. If some of the party stays far away enough that you judge that they don't need those rolls, that's fine.

Then, when either the players tell you they're ready, or the instant they are noticed, begin a combat sequence following the rules on page 189 — determine who is surprised, where everyone is, roll initiative, and go. Include the whole party in both the sneaking part and the first round of actual combat.

Answer 4

Yes, this is fine. When my group wants to do a stealth attack, this is how I usually run it (ie, I ask which of the PCs wants to be in the stealth group, and remind them that anyone that fails to stealth in the stealth group will cause the stealth attack to fail). As TJL commented, to make this work we need to formally consider the two groups of PCs to be two 'sides' in the conflict.

The DM might ask the less-stealthy PCs to make stealth checks as well, perhaps with advantage or some other bonus to reflect that they're farther away. The DM could elect to skip these checks if they think the PCs are far enough away. Which modifiers specifically should apply are determined by the DM depending on the exact circumstance, and we can't tell you in advance which modifiers would be right or wrong.

Answer 5

The first round of combat does not contain "only the two rogues and the two orks"; it contains everyone at the table.

Everyone rolls initiative and everyone takes actions on their turn.

The dwarfs outside the room might have to spend their first couple of turns moving in to the room where the orcs are, but they still take those turns at the appropriate place in the initiative order.

As far as surprise, if the orcs have no way to detect the presence of the two dwarfs (for example if they are a long distance away or if they are completely out of sight and hearing and smell) then they have certainly not noticed them as a threat at the start of combat. The only checks that need to be made are the two rogues' stealth checks and the orcs' perception checks.

If the dwarfs are just in the next room, it would be fair to get the players to make stealth checks with advantage. Even though the orcs can't see them, they still might hear them or smell them.