# Can a readied action or an attack of opportunity interrupt and thus cancel another action?

Can an attack of opportunity or a readied action interfere with another creature's action so that the creature, essentially, loses that action?

• Example 1: Nadir the rogue and Peake the bugbear are engaged in battle. Peake takes a standard action to ready, picking the action Attack the potion and the trigger when Nadir drinks the potion. Nadir takes a standard action to drink the potion. Peake's trigger is pulled, and Peake provokes an attack of opportunity from Nadir (that misses) and attacks the potion, destroying it.

However, Nadir didn't drink the potion. It was destroyed before he could drink it. Does Nadir lose his standard action trying to drink the nonexistent potion? Or can Nadir now take a different standard action?

• Example 2: Peake takes a standard action to make a sunder attempt against Nadir's rapier. Peake doesn't have anything special to help with sunder attempts, so Peake provokes an attack of opportunity from Nadir by making a Sunder attempt. Nadir makes the attack of opportunity and opts to make a disarm attempt against Peake. Nadir doesn't have anything special to help with disarm attempts, so Nadir provokes an attack of opportunity from Peake by making a disarm attempt. Peake makes a normal attack of opportunity against Nadir, dealing damage to the rogue. Nadir's attack of opportunity disarm attempt succeeds, and Peake's weapon clatters to the floor.

Does Peake make the sunder attempt as if he still wielded his weapon, everything happening simultaneously? Or does Peake's sunder attempt just not happen? Or must Peake continue with the sunder attempt despite the loss of his weapon? If so, can Peake opt to abort his sunder attempt now that he's disarmed? Or can Peake, upon losing his weapon, change his action?

NOTE: Please indicate whether your answer is based on RAW rules or more RAI definition since I am looking for the RAW ruling here. Thanks everyone Interesting thread.

Caution: This runs long. The short version? The game doesn't say. Play how you want.

The special initiative action ready, in part, at first says, "The action [that the creature that took the action ready picked] occurs just before the action that triggers it," but then the description continues, saying, "If the triggered action is part of another character's activities, you interrupt the other character. Assuming he is still capable of doing so, he continues his actions once you complete your readied action" (Player's Handbook 160).

One issue is that The triggered action occurs before the triggering action and The triggering action interrupts the triggered action are kind of incompatible. That is, the game explains only how a handful of actions—like counterspelling and distracting a spellcaster—can interrupt an action. The game leaves the rest of the ready action for the DM to adjudicate, including the pregnant statement After the triggered action, if he can, the subject that triggered the actions continues his actions. (Even the Dungeon Master's Guide on Adjudicating the Ready Action (25–6) is little help!)

Another issue is that, to my knowledge, there's absolutely no good published example of how the ready action is intended to work except in that handful of specific instances described in the ready action itself. That is, there are combat examples in Sword and Fist, for instance, and in one a dude takes the ready action, but here's that example:

Druga anticipates a charge from Alarion, so both he and his warhorse prepare to attack Alarion’s mount when it approaches within range. Druga and his horse ready attack actions (Druga with his longsword, the warhorse with a hoof). (65 and italics preserved from the original)

That's it. And this example ain't like, for example, smashing an about-to-be-consumed potion. Likewise, the Web column Gamestoppers has folks take the special initiative action ready, but they only take it only so they can distract spellcasters. (It also doesn't help either that both sources of examples are for the unrevised game.)

Below are offered two of the schools of thought on the special initiative action ready. There are undoubtedly others, but these are the two that I've encountered most frequently in online forums. A DM should pick one or develop his own at a campaign's beginning lest fights ensue later on.

## Approach #1: A creature can ready an action so that the subject wastes its action

When a creature takes the action ready and picks an action then picks a trigger like When a subject does X, the creature takes the picked action when the subject's player says that the subject is going to do X. That is, when a creature takes the action ready, everybody essentially adds a step to any actions he or she takes: instead of just doing X, first, a creature claims it'll do X, then, second, the creature actually does X, and making the claim commits the subject to the action.

Thus, when a subject makes a claim that matches a creature's picked trigger, the trigger is pulled and the creature may take picked action. After the picked action is resolved, if the subject now can't do X, then the subject loses that action.

### Example 1

Peake the bugbear chieftain takes a standard action to take the ready action, picking the action Attack the potion and the trigger When Nadir tries to drink the potion. On her turn, Nadir claims that she'll take a move action that provokes attacks of opportunity to retrieve an item—the potion—then takes that action. Then Nadir claims she'll take a standard action that provokes attacks of opportunity to drink the potion. Peake's trigger is pulled, Peake makes an attack roll against the potion (AC 10 + its size modifier + Nadir's Dexterity modifier) and succeeds, destroying the potion. Nadir, committed to the act of drinking the potion via her claim, loses her standard action.

If the DM just tells players when a creature takes the action ready and what the creature picked as a trigger, then claims needn't be formalized, but if the DM keeps the trigger secret, this DM recommends prevent arguments by formalizing claims.

## Approach #2: Often a creature can ready an action so that the subject can't take that action, but the subject can still take a different action; however, some specific actions can be interrupted so that they're wasted

When a creature takes the action ready and picks an action then picks a trigger like When a subject does X, the creature takes the picked action when the subject does X. If the game has specific rules for interrupting X, then those rules are used (e.g. casting a spell). If the game lacks rules for interrupting X, the creature's picked action occurs before X and, upon the resolution of the creature's picked action, the subject can do something else, the subject opting for a different action than the subject originally intended in light of changed battlefield conditions.

Yes, this is more than a little opaque and, beyond that, a little nuts, too, as it borders on, like, Schrödinger's action territory, but bear with me as I offer an example:

### Example 2

Peake the bugbear chieftain takes a standard action to take the ready action, picking the action Attack the potion and the trigger When Nadir drinks the potion. On her turn, Nadir drinks the potion. Peake's trigger is pulled, but there are no specific rules for interrupting drinking a potion, so Peake's picked action occurs before Nadir drinks the potion. Peake makes an attack roll against the potion (AC 10 + its size modifier + Nadir's Dexterity modifier) and succeeds, destroying the potion. It's still Nadir's turn, and Nadir's taken no actions—she didn't actually drink the potion! She takes a full-round action to make a full attack against Peake.

Until they wrap their heads around it—and sometimes even afterward—, this makes folks awfully uncomfortable. The theory goes like this: When a creature takes the action ready, it's establishing what it wants to do, but the creature has no control over the subject of the ready action. So when Peake took that ready action and in response to the picked trigger took the picked action, Peake only performed his action. While the subject may be—and, in this case, was—affected by it, the subject is free to adapt to it and change actions now that the battlefield has changed.

Why this makes folks uncomfortable should be clear, but just in case, let me state it: What folks tend to want to do is not just respond to a foe doing X but both respond to the foe doing X and prevent the foe from doing X. Unfortunately, most of the game's actions don't have rules for both: for example, casting a spell does, but swinging a sword, drinking a potion, or even moving don't. Explaining this may initially result in exchanges like this:

Player: But Peake broke Nadir's potion when she went to drink it, so Nadir should lose her standard action.
DM: But Nadir never took that standard action to drink the potion; Peake took his action first, triggered by what would have been Nadir drinking the potion. Nadir totally would've drunk that potion had Peake not broken it, but, after resolving Peake's attack against the potion, it's still Nadir's turn, and she's taken no actions, so Nadir makes a full attack.
Player: So if Peake hadn't've broken the potion, Nadir would've taken a standard action to drink it, and Peake wouldn't be staring down Nadir's sword right now?
DM: That's accurate, yes. Peake can't know how someone will react to changing battlefield conditions. Peake only knows what he'll do.

This reading is built on a couple of different ideas. First, the rules don't mention the existence of a general claim step. (The special attack charge, for example, does have a claim step in which the creature picks the target of his charge; most events don't.) That is, folks typically really do just plunge ahead and do X; only under specific circumstances—and the ready action isn't described as one of those circumstances—does the game require folks to first announce their intention to do X then actually do X.

Second, a creature can't forfeit an action it didn't take. For example, Nadir didn't drink the potion; I mean, she totally would've but, ultimately, she didn't. Narrating this gets a little complicated, but comes down to the DM saying, "Had the creature's picked actions not prevented the subject from taking its action, the subject would've gone through with the action the creature prevented." That may seem a small consolation to the creature that's now on the receiving end of the subject's full attack, for example, but if the DM makes sure everybody understands that the special initiative action ready does not typically let the creature mandate the subject's actions but, instead, lets the creature control its own actions, things may go a little more smoothly. But, yes, in the end, this approach is much more difficult than just creating a claim phase.

Note: The second approach is tacitly endorsed (seriously, tilt your head and squint a lot) by the Dragon #315 Wizards Workshop column "Sage Advice: Combat and Casting: Official Answers" with the exchange beginning, "Suppose a fighter and an archer go at the same initiative.…" (109) and that's repeated almost verbatim by the Main FAQ (74). The Sage at the time is co-designer Skip Williams. This semiendorsement, of course, doesn't make the second approach any more playable.

# "What about attacks of opportunity?"

Attacks of opportunity specifically and always interrupt the action that was taken:

An attack of opportunity “interrupts” the normal flow of actions in the round. If an attack of opportunity is provoked, immediately resolve the attack of opportunity, then continue with the next character’s turn (or complete the current turn, if the attack of opportunity was provoked in the midst of a character’s turn). (Player's Handbook 137)

Nobody knows what this means either because the same problem with attacks of opportunity exist with the special initiative action ready: the game is mostly silent on what happens if the interruption should prevent an action that a creature's presumably in the middle of!

This reader suspects most folks use a Magic: The Gathering-style last-in-first-out (LIFO) stack that sees the final attack of opportunity in a cascade happen first then the next-to-last and successively earlier ones occur in order approaching the original event. Then, if at any point a creature is unable to complete an action, the cascade ends and the LIFO stack is cleared. Here once more is the question's example, absent any resolutions:

Peake takes a standard action to make a sunder attempt against Nadir's rapier. Peake doesn't have anything special to help with sunder attempts, so Peake provokes an attack of opportunity from Nadir by making a Sunder attempt. Nadir makes the attack of opportunity and opts to make a disarm attempt against Peake. Nadir doesn't have anything special to help with disarm attempts, so Nadir provokes an attack of opportunity from Peake by making a disarm attempt.

To resolve this situation using the LIFO stack approach, Peake resolves his normal it'll-deal-damage attack of opportunity due to Nadir's disarm attempt first; if this kills her, the stack's cleared. If not, then Nadir resolves her disarm attack of opportunity due to Peake's sunder attempt next; if Nadir disarms Peake of his weapon that was used to make the sunder attempt, the stack's cleared. If not, then Peake makes his sunder attempt; when that resolves, the stack's cleared.

The alternative approach allows changing an action if it hasn't yet been taken. For example, a creature can, due to battlefield conditions changing, change its action as if it'd not taken the original action… because it hasn't yet taken that action! Changing an action in this way, however, doesn't obviate any of attacks of opportunity already provoked—those still occur—and, in fact, with the new action, the creature can provoke even more attacks of opportunity!

For example, once his weapon's at Nadir's feet, Peake, if his actions permit, could, instead of making the sunder attempt, take a move action to move up to his speed, and, if he leaves or moves within Nadir's threatened area normally, he'll provoke another attack of opportunity from Nadir. Again, like the second approach to readying an action, this may just feel wrong to players used to claims committing creatures to actions rather than actions committing creature to actions.

Once again, the DM should explain how things work in the campaign before the campaign's beginning lest players' expectations be violated during play.

Note: I'd not realized until after composing this answer that the Main FAQ endorses the LIFO approach by name in the Main FAQ in the exchange beginning, "Is it possible for an attack of opportunity to provoke an attack of opportunity?" (69-70). Unfortunately, my personal notes don't detail if this ruling has a provenance besides the Main FAQ itself.

It may interest some readers that Player's Option: Combat & Tactics (1995) for Advanced Dungeons & Dragons, 2nd Edition from which comes the attacks of opportunity concept has an attack of opportunity only and exclusively being a for-damage regular ol' melee attack—other kinds of attacks like disarm and trip had to be made on a creature's turn. Totally without proof and as utterly baseless speculation, this reader imagines that the phrase "or even as an attack of opportunity" was added at the very last minute to the Player's Handbook (2000) table Actions in Combat—and never actually playtested—by an enterprising editor thinking Meh… What harm could it do? and gamers have been paying the price ever since.

## It is implied (but not conclusively stated for all cases) that the interrupted action is canceled or lost, unless they can still reasonably complete the action.

The SRD states, in part:

The action occurs just before the action that triggers it. If the triggered action is part of another character’s activities, you interrupt the other character. Assuming he is still capable of doing so, he continues his actions once you complete your readied action.

And specific to spellcasters:

If you damage the spellcaster, she may lose the spell she was trying to cast (as determined by her Concentration check result).

...

...you can cast the spell as a counterspell and automatically ruin the other spellcaster’s spell.

This implies that the two options are to either be interrupted (thus losing or canceling the action), or to continue with the previously planned action.

Thus in a chain of interrupting actions, the last valid action is king and wins, canceling all the others, unless one or more of the interrupted actions could still be reasonably completed.

Note that this is all taking place in 6 second rounds. It is rather unlikely to be able to change one's action and actually pull it off in less than the span of 6 seconds. Most people can't even think that fast, let alone move around much, not to mention actually planning a new course of action and nearly instantly carrying it out. Also note on the other hand that D&D is note exactly true-to-life, so expecting the rules to be true-to-life is rather silly.

Having said that, at high levels, where characters have become basically super-heroic, then the concept is much less of an issue. Regardless of level, this is (most likely) a fantasy world, so it's not that big a deal to allow the players to re-choose their actions once interrupted, especially combat types. They already have enough trouble keeping up with magic types as it is.

In conclusion, it seems strongly implied that the countered action is in fact canceled or negated. As a personal opinion, I would certainly allow combat types to replace a canceled combat action with another logical combat action appropriate to the situation.

The rule says

Please note, the readied action is a response to that condition even though the action occurs just before the action that triggers it. The only way both statements can be true* is if the rule is intended to imply the triggering action is started, triggering the readied actor to respond by performing that readied action before the action that triggered it can complete.

*:Short of some time travel explanation.

Also note, Assuming he is still capable of doing so, he continues his actions once you complete your readied action. It does not say starts his actions it says continues. Short of a couple of special cases (starting a full round action as a standard action and full round casting time spells), actions are discrete and cannot be broken up. There's no mechanism in the rules for reclaiming a partially spent action, even if it was unable to complete. The action was used or consumed or spent starting the action, regardless of whether or not it completes.

In the PHB version, it has the same text plus this example:

In practice. Example 1.

Nadir the rogue and Peake the bugbear are engaged in battle. Peake takes a standard action to ready, picking the action Attack the potion and the trigger when Nadir drinks the potion. Nadir takes a standard action to drink the potion. Peake's trigger is pulled, and Peake provokes an attack of opportunity from Nadir (that misses) and attacks the potion, destroying it.

Peake's turn - ready action to attack potion

Nadir's turn - Uses standard action to drink a potion

This action is what Peake readied for so Peake destroys Nadir's potion leaving Nadir unable to complete his action to drink the potion. If Nadir has any remaining actions (move, swift, et al), Nadir may now take them, but Nadir already spent his standard action attempting to drink the potion.

Round continues with whoever's after Nadir.

The next example addresses Attacks of Opportunity. The key rule here is

If an attack of opportunity is provoked, immediately resolve the attack of opportunity, then continue with the next character’s turn (or complete the current turn, if the attack of opportunity was provoked in the midst of a character’s turn).

Example 2

Peake takes a standard action to make a sunder attempt against Nadir's rapier. Peake doesn't have anything special to help with sunder attempts, so Peake provokes an attack of opportunity from Nadir by making a Sunder attempt. Nadir makes the attack of opportunity and opts to make a disarm attempt against Peake. Nadir doesn't have anything special to help with disarm attempts, so Nadir provokes an attack of opportunity from Peake by making a disarm attempt. Peake makes a normal attack of opportunity against Nadir, dealing damage to the rogue. Nadir's attack of opportunity disarm attempt succeeds, and Peake's weapon clatters to the floor.

On Peake's turn he uses a standard action to make a sunder attempt

This provokes an Attack of Opportunity from Nadir

Nadir attempts a disarm with his Attack of Opportunity

This provokes an Attack of Opportunity from Peake

Peake attacks Nadir with his Attack of Opportunity and hits and Nadir takes damage.

Nadir disarms Peake (continuing his Attack of Opportunity)

Peake is no longer able to continue with his sunder attempt.

It is now just after Peake's standard action. If he has any remaining actions (move, swift, et al), he may take them, otherwise, continue with the next up in initiative order. At this point, both Peake and Nadir have consumed one Attack of Opportunity. Depending on where we were in the round to begin with, at least Peake has used his actions for this round.

• In short, is it accurate to say that this answer supports the idea that A creature can ready an action so that the subject wastes its action? – Hey I Can Chan May 18 '18 at 15:47
• So, using the example, Peake readies the action Attack the potion and the trigger when Nadir tries to drink the potion. Then, when Nadir takes the action I drink my potion, Peake pulls the trigger and destroys the potion. Nadir is, however, still committed to drinking the potion, and, now, because she can't drink the potion—even though she hasn't drunk the potion—, that action is essentially wasted, lost, forfeited, cancelled, or whatever verb's preferred. Is that accurate? (Just to be clear, I'm not playing Gotcha! or anything! I'm honestly just seeing if we're on the same page.) – Hey I Can Chan May 18 '18 at 16:25
• So even when there aren't rules for interrupting an action—i.e. when "[t]he action occurs just before the action that triggers it"—this answer would still have the creature that started the triggering action finish the triggering action? Is that accurate? (I think it'd be awesome if this answer addressed the examples directly!) – Hey I Can Chan May 18 '18 at 17:01
• I think you have to read it in context. We're given two facts. Readied actions are a response and they occur before the action that triggered them. You have to make those two congruent. – Wyrmwood May 18 '18 at 22:25
• It isn't a "declaration" that gets responded too, it's the action itself. – Wyrmwood May 21 '18 at 23:00

I'm sure it would be clearer if using another example than drinking a potion. And I add because maybe it still can bring some more insight to this thread may help others too. Based on the premise that (phb. p.304)

action: A character activity. Actions are divided into the fol- lowing categories, according to the time required to perform them (from most time required to least): full-round actions, standard actions, move actions, and free actions.

And that (Rule Compendium p. 110) the phb version of ready action was changed, probably due to the word "action" which is now "whatever"

HOW TO READY Readying is a standard action that doesn’t provoke attacks of opportunity, though the action that you ready might provoke attacks of opportunity when you take that action. You can ready a standard action, a move action, a swift action, or a free action. To do so, you must specify what you want to do and the conditions under which you will do so. Then, any time before your next turn, you can take the readied action in response to those conditions. The action occurs just before whatever triggers it. If the triggering condition is part of another creature’s activities, you interrupt that creature’s turn. Assuming the interrupted creature is still capable of doing so, it continues its turn once you complete your readied action.(bold words added by me)

Let's use a ready action with the trigger "when Peake turns the corner" and set the action "I trip Peake" Peake has 15' to move before turning the corner so he starts his move action, move up 10' turns the corner (15') which triggers the readied action. The trip attempt [the action] is made with a weapon and the attempt succeed. Peake falls prone 15' away from when he started his move action. He can't complete his action but he can complete his turn by, let's say, standing up. As the previous understanding would suggest that Peake would be able to do his move action all over again, this would mean he would be back 15' and prone to the beginning of his turn as his move action, not being able to complete would be able to start it again and choose another move action.

With the rule as it is written and the flow of actions and turns, and the concept of simultaneous activity from p. 71 of compendium

SIMULTANEOUS ACTIVITY When playing out a combat scene or some other activity for which time is measured in rounds, remember that all the combatants’ actions occur simultaneously. The combatants’ acting in turn according to the initiative count is a situation necessary for order in game play, but it’s an abstraction. This sequential order of play can lead to situations when something significant happens to a combatant at the end of that creature’s turn but before other creatures have acted in the same round. It’s up to the DM whether other combatants who have yet to act during the round can react to an event that happens to another combatant in this way.

I would definitely follow the rule and have the action that triggered the readied action (as defined above) is wasted since it the action is in doing (as my example of moving) and the only way you can word it to ensure that the readied action resolve before the actual trigger is how they did it in the compendium. One must understand that the goal is to stop a creature from doing something or at least ensure your action happens before the other in the sequential order of things even all of it happens pretty much at the same time.

For the attack of opportunity, compendium p. 19 worded it the same way with interrupting "whatever" provoked it

An attack of opportunity interrupts the normal fl ow of actions in the round. If an attack of opportunity is taken, immediately resolve that attack of opportunity, then continue with whatever was happening when the attack of opportunity was provoked

So rule is the same. Even though they didn't specify "if able to do so", of course if the creature is disabled it won't be able to complete what provoked the aoo.

• I think the major difference is that an Attack of opportunity interrupts the player's ACTION within his turn, while a ready action interrupts the player's TURN, not the action since it occurs BEFORE the action that triggered it. Thus an attack of opportunity can have an impact on the current action it is unterrupting, but not a ready action since the action did not occur yet. – KilrathiSly Dec 1 '18 at 22:15
• BUT: there seems to be some exceptions possible when the action relates to movement from square to square, but even then the tripped Peakes would still have his remaining movement left even if prone, The ready action would in now way 'cancel' his remaining movement, Peake could try to stand up as a free action (compendium P94, Tumble check DC35) and if successfull, would just continue his movement like nothing happened, could even change his destination and retreat back from where he came. – KilrathiSly Dec 1 '18 at 22:19
• @KilrathiSly the compendium does not state that the readied action is resolved before the other's action but before whatever triggered it which is very different as action has its own definition. Also, the reason the rule is written so to differentiate attack of opportunity and readied action is that you can't interrupt the other's turn with an attack of opportunity since it is a non action attack not taken during your turn while the readied action is truly your action that is interrupting the other's turn... Which also ends up changing your initiative order. – jonDraco Dec 1 '18 at 22:35
• And for your example of Peake with tumble skill, yes if he succeeds as it is also stated in the readied action that he can continue If he is capable of doing so. If he does not succeed his check then he can't continue his action which still support the example. – jonDraco Dec 1 '18 at 22:45
• From the official indications of WotC, if both the PHB rule and compendium rule contradicts themselves, the PHB has preseance. – KilrathiSly Dec 6 '18 at 1:08