Rules of the Game
Attacks of Opportunity (Part One)
By Skip Williams

If there's one question players and DMs dread, it's this one: Does that provoke an attack of opportunity? Arguments about attacks of opportunity happen frequently, mostly because misconceptions and misunderstandings about them abound.

Why Attacks of Opportunity at All?

The D&D game uses its attack of opportunity rules to add some spice to combat. These rules offer characters more options in combat than just standing there and exchanging attacks with foes, while at the same time making sure that characters involved in a fight have a proper appreciation for the dangers they face.

Many rules in the game would be very different (and probably much harder to use) without attacks of opportunity to balance them. The rules for spellcasting, ranged attacks, movement, and special attack actions such as disarming, grappling, and tripping all depend on the existence of attacks of opportunity.

Attack of Opportunity Basics

As is often the case in the D&D game, the actual rules for attacks of opportunity aren't hard to grasp -- it's the exceptions to those rules that prove difficult to handle.

You can provoke an attack of opportunity in the D&D game in two situations, and here they are:

  • You provoke an attack of opportunity when you're in a square on the battlefield that a foe threatens and you leave that square.

  • You provoke an attack of opportunity when you're in a square on the battlefield that a foe threatens and you take some other action that provokes an attack of opportunity.

The diagram on page 138 of the Player's Handbook shows these two principles at work.

When Is a Square Threatened?

Since an attack of opportunity involves a threatened square, a short discussion of exactly when a square is "threatened" is in order:

  • A creature threatens all squares into which it can make an armed melee attack.

To be "armed," a creature must wield at least one weapon, either a natural weapon or a manufactured weapon. Most creatures have at least 5 feet of reach, so they threaten all squares adjacent to their spaces (including diagonally). If a creature has a reach of more than 5 feet (by virtue of its size or because it wields a reach weapon, or both) it threatens more squares.

A creature can attack into its own space, and so it threatens that square or squares as well. See page 149 in the Player's Handbook for a discussion of a creature's space.

A Few More Basics

Only a few more rules round out the basics for attacks of opportunity:

  • An attack of opportunity is a melee attack.

You can't use a ranged weapon, a spell, a special ability, or a magic item in an attack of opportunity (though there are a few exceptions, which we'll consider next time).

  • An attack of opportunity is something a creature does during another creature's turn.

As such, the attack of opportunity interrupts the normal flow of action during the turn. Also, because it isn't the attacking creature's turn, there are strict limits on what it can do.

Common Misconceptions About Attacks of Opportunity

Most difficulties with attacks of opportunity can be traced to one of three widespread misconceptions about attacks of opportunity and how they work. You can make the vast majority of your difficulties with attacks of opportunity vanish simply by knowing that these misconceptions exist and avoiding them yourself.

Common Misconception #1: You provoke an attack of opportunity when you're moving and you enter a threatened square.

  • You provoke an attack of opportunity when you leave a threatened square, not when you enter it. Sometimes you'll provoke an attack of opportunity when moving closer to a foe (see the section on Reach below), and you'll also do so if you try to enter a square that a foe already occupies.

Common Misconception #2: What you do later in your turn can affect whether you provoke an attack of opportunity when you leave a threatened square.

  • If you get out of threatened square alive, you don't have to worry about attacks of opportunity later -- unless you've moved into another square that a foe threatens.

Common Misconception #3: Attacks of opportunity happen after the actions that trigger them.

  • Resolve an attack of opportunity before you resolve the action that triggered it, not after. Sometimes, the attack of opportunity will prevent the triggering action (such as when the attack of opportunity proves lethal to a moving character). If someone tries something that provokes an attack of opportunity, the attack of opportunity happens first. Attacks of opportunity you make in response to a foe's spellcasting or use of a spell-like ability are an exception (see the Making an Attack of Opportunity section), as is moving into a space another creature occupies.

What's Next?

Next time, we'll go beyond the basics and consider how some of the game's other rules interact with the rules for attacks of opportunity.

About the Author

Skip Williams keeps busy with freelance projects for several different game companies and was the Sage of Dragon Magazine for 18 years. Skip is a co-designer of the D&D 3rd Edition game and the chief architect of the Monster Manual. When not devising swift and cruel deaths for player characters, Skip putters in his kitchen or garden (rabbits and deer are not Skip's friends) or works on repairing and improving the century-old farmhouse that he shares with his wife, Penny, and a growing menagerie of pets.


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