Can a character power attack before making an attack of opportunity?

Question

In a recent game, a scenario arose where a character lost initiative but subsequently was granted an attack of opportunity (had Combat Reflexes) by an enemy. There was a follow up discussion about whether or not that character could power attack before the AOO.

Power Attack reads:

On your action, before making attack rolls for a round, you may choose to subtract a number from all melee attack rolls and add the same number to all melee damage rolls. This number may not exceed your base attack bonus. The penalty on attacks and bonus on damage apply until your next turn.

The thought was that this was before the characters attack rolls and thus could be applied (and would last until their next turn). Similarly, if a character on their initiative did a double move then later (but before their next initiative) an enemy provoked an attack of opportunity, it was thought that the character could also power attack then, 'before making attack rolls for a round'.

Notably Power Attack says "On your action," not "On your turn,". Thusly, I suspect the question could be answered, by the answer if an attack of opportunity (or the melee attack it generates) is an action or not, however there may be other answers/evidence here. Neither me nor my friend could find anything definitively answering this in the PH or FAQ. I am hoping someone else knows of a ruling to this.

I prefer RAW answers as I suspect other would just be opinion, however am not adding that tag. Thanks in advance.

Further thoughts:

• The glossary supports that all attacks are actions ["attack" pg 305 - 3.5 PHB:]

Any of numerous actions intended to harm, disable, or neutralize an opponent.

However, this could also describe any number of non-melee attacks (which is what AOO gives).

• AOO is not listed anywhere in the combat actions chart as an action. It is listed as an exception (THE COMBAT ROUND on pg 138 of the PHB).

When a character's turn comes up in the initiative sequence, that character performs his entire round's worth of actions. (For exceptions, see Attacks of Opportunity and Special Initiative Actions).

• Possibly related Standard action maneuver AoO. Specifically the differentiation between the melee attack an AOO gives and a normal "action".

• STANDARD ACTIONS pg 139 PHB

"Attack - Making an attack is a standard action."

Obviously not the case here, but supports the fact it's an action OR(/and) supports the fact that since it's not a standard action, the AOO melee attack isn't an action as defined here.

• ATTACKS OF OPPORTUNITY pg 137 PHB

"...combatants near her can take advantage of her lapse in defense to attack her for free. These free attacks are called attacks of opportunity."

Clarifies it's an attack and speaks that it's free (free action?).

Answer 1

No.

You have to choose to Power Attack on your turn as part of your attack action:

On your action, before making attack rolls for a round...

And the AoO rules say...

Attack of Opportunity

You threaten all squares into which you can make a melee attack, even when it is not your action.

Attacks of opportunity are special attacks -- they are not a type of action.

When it is your action (your turn), you can choose to make a Power Attack, before you make your attack rolls. You then get the Power Attack bonus for all melee attacks until the beginning of your next turn. This means you do (and must) apply your Power Attack bonus to an attack of opportunity, but only for an AoO made after the action in which you made a Power Attack and before your next turn.

Since it may not be obvious based on the comments I'm getting, the "on your action" language is almost definitely an accidental hold-over from the 3e rules, as mentioned in KRyan's answer. It is not intended to mean on any action, but specifically on your turn.

Answer 2

In D&D 3.0, “your action” meant your turn, and that is the only meaning I can attribute to the phrase’s use here, too. It looks like a pure editing mistake, using the old term for turn here. Or maybe initially they intended 3.5 to continue using action in that way, even though that’s very confusing.

Either way, I would treat Power Attack as something you can set on your own turn, before making any attacks, and your choice affects all attacks from then until your next turn, including attacks of opportunity, with no chance to change the value you set it to.

Answer 3

Both Combat Expertise and Power Attack use the same term "action", which clearly leaves room for confusion. Power Attack is in effect

until your next turn

which does seem to support starting and ending on your turn, while Combat Expertise starts with

When you use the attack action or the full attack action in melee

and is in effect

until your next action

leaving more room for attributing to any attack "action". As KRyan points out, "attack action" is really short-hand for "attacking as a standard action", just as full attack action is short-hand for "attacking as a full round action".

However, if you assume it really does mean any action, this would allow a player to benefit from the bonuses from Power Attack or Combat Expertise on the first attack in a full-round attack action, then allow the player to "turn off" the disadvantages before the last attack. This would essentially remove the disadvantages from either tactic, and thus I suspect the intent in both cases was to start "on your turn" and end "on your next turn".