Yagura:SRD:Attack of Opportunity

Attacks of Opportunity

Sometimes a combatant in a melee lets his guard down. In this case, combatants near him can take advantage of his lapse in defense to attack him for free. These free attacks are called attacks of opportunity, or AoOs.

Threatened Squares

You threaten all squares into which you can make a melee attack, even when it is not your action. Generally, that means everything in all squares adjacent to your space (including diagonally). An enemy that takes certain actions while in a threatened square provokes an attack of opportunity from you. If you’re unarmed or armed with a non-melee weapon (such as a bow), you don’t normally threaten any squares and thus can’t make AoOs.

Reach Weapons

Most creatures of Medium or smaller size have a reach of only 5 feet. This means that they can make melee attacks only against creatures up to 5 feet (1 square) away. However, Small and Medium creatures wielding reach weapons threaten more squares than a typical creature. In addition, most creatures larger than Medium have a natural reach of 10 feet or more.

Provoking an Attack of Opportunity

Two kinds of actions can provoke attacks of opportunity: moving out of a threatened square and performing an action within a threatened square.

Moving

Moving out of a threatened square (but not into a threatened square) usually provokes an attack of opportunity from the threatening opponent. There are two common methods of avoiding such an attack: the 5-foot-step and the Withdraw action (see Table: Actions in Combat).

Performing a Distracting Act

Some actions, when performed in a threatened square, provoke attacks of opportunity as you divert your attention from the battle. Table: Actions in Combat notes many of the actions that provoke AoOs.

Remember that even actions that normally provoke AoOs may have exceptions to this rule.

Making an Attack of Opportunity

An attack of opportunity is a single melee attack, and you can only make one per round. You don’t have to make an AoO if you don’t want to.

An experienced character gets additional regular melee attacks (by using the full attack action), but at a lower attack bonus. You make your attack of opportunity, however, at your normal attack bonus—even if you’ve already attacked in the round.

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

Economy of Opportunity

Each character can make only one attack of opportunity per round. Some abilities and feats increase the number of AoOs you have available. If you have a Base Attack Bonus high enough to warrant gaining additional attacks, you also get additional AoOs. So a character with a BAB of +6 can make 2 AoOs each round. A character with a BAB of +11 can make 3, and a character with 16 can make 4.

This does not let you make more than one attack for a given opportunity, but if the same opponent provokes two attacks of opportunity from you, you could make two separate AoOs (since each one represents a different opportunity). Moving out of more than one square threatened by the same opponent in the same round doesn’t count as more than one opportunity for that opponent. All these attacks are at your full normal attack bonus.