The Order of Combat
A typical combat encounter is a clash between two sides, a flurry of weapon swings, feints, parries, footwork, and spellcasting. The game organizes the chaos of combat into a cycle of rounds and turns. A round represents about 6 seconds in the game world. During a round, each participant in a battle takes a turn. The order of turns is determined at the beginning of a combat encounter, when everyone rolls initiative. Once everyone has taken a turn, the fight continues to the next round if neither side has defeated the other.
Combat Step by Step
1. Determine surprise. The GM determines whether anyone involved in the combat encounter is surprised.
2. Establish positions. The GM decides where all the characters and monsters are located. Given the adventurers' marching order or their stated positions in the room or other location, the GM figures out where the adversaries are--how far away and in what direction.
3. Roll initiative. Everyone involved in the combat encounter rolls initiative, determining the order of combatants' turns.
4. Take turns. Each participant in the battle takes a turn in initiative order.
5. Begin the next round. When everyone involved in the combat has had a turn, the round ends. Repeat step 4 until the fighting stops.
A band of adventurers sneaks up on a bandit camp, springing from the trees to attack them. A gelatinous cube glides down a dungeon passage, unnoticed by the adventurers until the cube engulfs one of them. In these situations, one side of the battle gains surprise over the other.
The GM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the GM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (Perception) score of each creature on the opposing side. Any character or monster that doesn't notice a threat is surprised at the start of the encounter.
If you're surprised, you can't move or take an action on your first turn of the combat, and you can't take a reaction until that turn ends. A member of a group can be surprised even if the other members aren't.
Initiative determines the order of turns during combat. When combat starts, every participant makes a Dexterity check to determine their place in the initiative order. The GM makes one roll for an entire group of identical creatures, so each member of the group acts at the same time.
The GM ranks the combatants in order from the one with the highest Dexterity check total to the one with the lowest. This is the order (called the initiative order) in which they act during each round. The initiative order remains the same from round to round.
If a tie occurs, the GM decides the order among tied GM-controlled creatures, and the players decide the order among their tied characters. The GM can decide the order if the tie is between a monster and a player character. Optionally, the GM can have the tied characters and monsters each roll a d20 to determine the order, highest roll going first.
On your turn, you can move a distance up to your speed and take one action. You decide whether to move first or take your action first. Your speed--sometimes called your walking speed--is noted on your character sheet.
The most common actions you can take are described in the "Actions in Combat" section later in this chapter. Many class features and other abilities provide additional options for your action.
The "Movement and Position" section later in this chapter gives the rules for your move.
You can forgo moving, taking an action, or doing anything at all on your turn. If you can't decide what to do on your turn, consider taking the Dodge or Ready action, as described in "Actions in Combat."
Various class features, spells, and other abilities let you take an additional action on your turn called a bonus action. The Cunning Action feature, for example, allows a rogue to take a bonus action. You can take a bonus action only when a special ability, spell, or other feature of the game states that you can do something as a bonus action. You otherwise don't have a bonus action to take.
You can take only one bonus action on your turn, so you must choose which bonus action to use when you have more than one available.
You choose when to take a bonus action during your turn, unless the bonus action's timing is specified, and anything that deprives you of your ability to take actions also prevents you from taking a bonus action.
Other Activity on Your Turn
Your turn can include a variety of flourishes that require neither your action nor your move.
You can communicate however you are able, through brief utterances and gestures, as you take your turn.
You can also interact with one object or feature of the environment for free, during either your move or your action. For example, you could open a door during your move as you stride toward a foe, or you could draw your weapon as part of the same action you use to attack.
If you want to interact with a second object, you need to use your action. Some magic items and other special objects always require an action to use, as stated in their descriptions.
The GM might require you to use an action for any of these activities when it needs special care or when it presents an unusual obstacle. For instance, the GM could reasonably expect you to use an action to open a stuck door or turn a crank to lower a drawbridge.
Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else's. The opportunity attack, described later in this chapter, is the most common type of reaction.
When you take a reaction, you can't take another one until the start of your next turn. If the reaction interrupts another creature's turn, that creature can continue its turn right after the reaction.