Opportunity Attacks, Walking Away From a Fight

The wizard stands next to a goblin and wants to be somewhere else. The table asks the same question every week: can I just walk away? You can. The goblin gets a swing at you first, unless you plan for it. Here is the whole rule, from SRD 5.2.1.

The rule in one sentence

The SRD puts the danger plainly:

If you move heedlessly past your foes, you put yourself in danger by provoking an Opportunity Attack.

And the trigger, word for word:

You can make an Opportunity Attack when a creature that you can see leaves your reach. To make the attack, take a Reaction to make one melee attack with a weapon or an Unarmed Strike against that creature. The attack occurs right before it leaves your reach.

Three things in there decide almost every ruling.

Leaving, not moving. The trigger is leaving the reach. Circling a goblin while staying within 5 feet of it provokes nothing. Walking out of that 5 feet does.

You must see it. A creature you can't see slips away free.

One melee attack, before it goes. The swing lands while the target is still in reach. A bow can't make an Opportunity Attack; a sword, an axe or a fist can.

It costs your Reaction

An Opportunity Attack is the most common Reaction in the game, and Reactions run out:

When you take a Reaction, you can't take another one until the start of your next turn.

So a goblin that swings at the fleeing wizard has nothing left when the rogue walks past a moment later. Two heroes leaving the same foe on the same round: the first one draws the attack, the second goes free. Order your retreats.

Reach sets the circle

A creature has a 5-foot reach and can thus attack targets within 5 feet when making a melee attack.

Some weapons stretch that circle. The SRD's Reach property:

A Reach weapon adds 5 feet to your reach when you attack with it, as well as when determining your reach for Opportunity Attacks with it.

The Glaive, the Pike and the Whip all carry it. A Fighter holding a Glaive controls a 10-foot circle, and a foe has to cross 10 feet of it to get clear, not 5.

Three ways out

Disengage. The clean exit:

If you take the Disengage action, your movement doesn't provoke Opportunity Attacks for the rest of the current turn.

It costs your action, so you walk away safe but do nothing else. For most characters that is the trade: safety or an attack, not both.

Disengage as a Bonus Action. Some creatures skip the trade. The Rogue's level 2 Cunning Action lets a Rogue take "Dash, Disengage, or Hide" as a Bonus Action. The Goblin Warrior's Nimble Escape does the same: "The goblin takes the Disengage or Hide action." That is why goblins stab and run in the same turn, and why your Rogue can too.

Get moved. The SRD lists the moves that never provoke:

You also don't provoke an Opportunity Attack when you Teleport or when you are moved without using your movement, action, Bonus Action, or Reaction. For example, you don't provoke an Opportunity Attack if an explosion hurls you out of a foe's reach or if you fall past an enemy.

A friend's shove, a blast that throws you, a teleport: all free. Only your own movement, action, Bonus Action or Reaction draws the swing.

The odds, worked out

Take the Goblin Warrior from the SRD: AC 15, HP 10, Scimitar "+4, reach 5 ft. Hit: 5 (1d6 + 2) Slashing damage."

The wizard walks away. Say the wizard has AC 12. The goblin's +4 needs an 8 or better on the d20: a 65% chance to hit. A hit averages 5.5 damage (the SRD rounds it to 5); a critical doubles the die. Across every roll the swing costs the wizard about 3.75 Hit Points on average. For a level 1 wizard, that is often half of everything.

The Fighter walks away. At AC 16 the goblin needs a 12: 45%. Armour buys the right to walk.

The goblin walks away from the Fighter. Use the Fighter from our character sheet post: Greatsword +5, 2d6 + 3 damage. Against AC 15 the Fighter needs a 10: a 55% chance to hit. The goblin has 10 HP, and 2d6 + 3 reaches 10 on 21 of the 36 rolls of 2d6. Add the critical (4d6 + 3 almost always clears 10) and the chance the goblin dies before it leaves is 34%. That is why the goblin spends a Bonus Action on Nimble Escape instead.

Turning it off

A few features shut the attack down at the source. The Barbarian's level 13 Staggering Blow leaves a target unable to "make Opportunity Attacks until the start of your next turn." The Open Hand Monk's Addle does the same until the start of the target's next turn. If your table has one of these, the whole party can walk past that foe.

At the table

1. Before you move, look for anything that can see you and has you in reach.
2. Ask yourself: is my action worth more than the Hit Points?
3. If not, Disengage, or let a friend shove you clear.
4. GMs: one Reaction per round. The second hero to leave walks free.

Players: the Rogue's Cunning Action is among the best features at level 2 for exactly this reason. GMs: goblins that stab and Disengage feel clever because they are using the rule as written.

The Book of Dice covers the d20 in Part I, The Object, and every way of rolling it in Part III.

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License.