In a game I am playing my GM decided that OAs happen in arbitrary order of the person doing the attack, instead of all at the same time — the order isn't even in the order of initiative. I was under the impression that all OAs happened simultaneously. Is this not the case?

The exact example is that a monk punched me and then a cleric cast "Command" (via Warcaster) on me, both using their OAs.

Aside, I argued that the Command spell shouldn't work in that circumstance for a bunch of reasons.

  1. The spell says it happens on your next turn, not the same turn.

  2. The command which was to "Grovel" put my character in danger, namely the Monk's punch or the fact that they were surrounded by enemies.

But assuming each opportunity attack was valid, is it correct that the opportunity attackers get to decide the order?


As it's your turn, you get to decide!

Xanathar's Guide to Everything contains an optional rule to help adjudicate this.

On page 77 (or here on DNDBeyond, if you own it there):

If two or more things happen at the same time on a character or monster's turn, the person at the game table-whether player or DM-who controls that creature decides the order in which those things happen. For example, if two effects occur at the end of a player character's turn, the player decides which of the two effects happens first.

So if multiple events would occur simultaneously (such as multiple opportunity attacks reacting to the same trigger), then the player whose turn it currently is gets to decide in what order those events occur for mechanical purposes.

  • \$\begingroup\$ Xanathar's ruling for simultaneous effects is probably the most applicable to this question currently. Nice call :) \$\endgroup\$ – HellSaint Jun 8 '18 at 1:43
  • \$\begingroup\$ Btw, Welcome to RPG.se! When you have time, take our tour. Other than that, as I've already mentioned, great call on the answer. \$\endgroup\$ – HellSaint Jun 8 '18 at 1:44

First, to avoid confusion with other versions but at the risk of being called a pedant, it is not an "Attack of Opportunity", it is an "Opportunity Attack."

Opportunity attacks (PHB p.195)

To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack interrupts the provoking creature’s movement, occurring right before the creature leaves your reach.

Assuming a number of creatures all get an opportunity attack on another creature they all interrupt the creature's movement, which occurs on a specific initiative order. It can then be said that all of the reactions tie on that initiative order and this is handled in the initiative rules:

Initiative (PHB p.189)

If a tie occurs, the DM decides the order among tied DM-controlled creatures, and the players decide the order among their tied characters. The DM can decide the order if the tie is between a monster and a player character. Optionally, the DM can have the tied characters and monsters each roll a d20 to determine the order, highest roll going first.

So in the case of tied reactions, if the creatures with the opportunity attacks are "monsters" the DM decides. If they are all player characters then the players decide. If it is a mix of "monsters" and PCs then the DM decides.

Optionally all the tied combatants can roll d20s (unmodified, the rules say nothing about a modifier) and go in that order. There is no guidance on what happens with another tie in this optional rule, but I think common sense would be to roll again between those who are tied until it is resolved.

  • \$\begingroup\$ What rule says interruptions occur in the initiative order? \$\endgroup\$ – kviiri Jul 21 '17 at 13:18
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    \$\begingroup\$ Read carefully. Protonflux says that the creature being attacked operates on initiative order, and all reacting creatures are considered "tied", then goes on to specify how ties are broken. In absence of rules to the contrary, it's a valid interpretation. \$\endgroup\$ – keithcurtis Jul 21 '17 at 14:23
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    \$\begingroup\$ This case is a little interesting. With the rules you posted, the Grovel command would have made OP fall prone and end their turn which wouldn't have made them leave the reach of the other attacker since Opportunity Attack occurs before they leave reach. Would that deny the monk their reaction since OP didn't leave their reach because he fell prone right then and there? \$\endgroup\$ – KumosAgosta Jul 21 '17 at 15:57
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    \$\begingroup\$ As the question points out, command takes effect on the target's next turn. \$\endgroup\$ – Marq Jul 21 '17 at 18:44
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    \$\begingroup\$ That may also merit another question, actually. \$\endgroup\$ – Marq Jul 21 '17 at 19:48

First, you have used "AoOs" when you mean "Reactions". The rules have this to say about Reactions:

Certain Special Abilities, Spells, and situations allow you to take a Special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else’s. The opportunity attack is the most common type of reaction.

When you take a reaction, you can’t take another one until the start of your next turn. If the reaction interrupts another creature’s turn, that creature can continue its turn right after the reaction.

The rules are completely silent on what happens if two creatures have their reactions triggered by the same event. Therefore, it is up to your DM to decide if they happen simultaneously and, if not, the order in which they happen.

It appears that your DM has decided that the creatures who have their reactions triggered can decide between them who goes first. I find this decision ... problematical but it was not my decision to make. However, now that you know this is the way reactions work, I am sure you and your fellow players can turn this to your advantage in future combats.

  • \$\begingroup\$ roll 1d6, each side, and see who gets to go first. It's worked since 1974 \$\endgroup\$ – KorvinStarmast Mar 8 '19 at 5:25

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