D&D Combat Rules: Full Breakdown

Combat in Dungeons & Dragons operates as a structured subsystem governing hostile encounters between player characters, non-player characters, and monsters. The rules codified in the fifth edition (5e) Player's Handbook and Dungeon Master's Guide establish a turn-based framework that resolves attacks, movement, spellcasting, and special actions through dice rolls, ability modifiers, and positional mechanics. This page serves as a comprehensive reference for the mechanical architecture of D&D combat, its classification boundaries relative to adjacent rule subsystems, and the tensions inherent in its design.

• Definition and Scope
• Core Mechanics or Structure
• Causal Relationships or Drivers
• Classification Boundaries
• Tradeoffs and Tensions
• Common Misconceptions
• Checklist or Steps (Non-Advisory)
• Reference Table or Matrix
• References

Definition and Scope

The combat rules in D&D 5e define a discrete encounter mode that begins when hostile creatures act against one another and ends when one side is defeated, flees, or negotiates a cessation. Combat is distinguished from exploration and social interaction — the other two pillars of play described in Chapter 8 of the 5e Player's Handbook (Wizards of the Coast, 2014). For a broader view of how these pillars interrelate, see the conceptual overview of recreation as a structured activity.

Combat operates on a 6-second round cycle. Each round contains one turn per combatant, during which a creature can take an action, a bonus action (if a feature grants one), movement up to its speed, and one reaction (which may occur on any turn within the round). A typical combat encounter lasts 3–5 rounds, though variance is high depending on party level, enemy count, and tactical complexity.

The scope of combat rules encompasses:

• Initiative determination via Dexterity checks, establishing turn order
• Attack resolution through d20 rolls compared against Armor Class
• Damage application reducing hit points toward 0
• Condition tracking for effects such as stunned, restrained, and frightened per the conditions rules
• Death resolution when a creature reaches 0 HP, governed by death saving throws

Core Mechanics or Structure

The Action Economy

The action economy is the foundational structural concept of 5e combat. Each turn grants exactly 1 action, 1 bonus action (if applicable), movement equal to the creature's speed stat (typically 30 feet for Medium humanoids), a free object interaction, and 1 reaction per round. The actions, bonus actions, and reactions framework determines what a creature can accomplish per turn.

Standard actions available to all creatures include: Attack, Cast a Spell, Dash, Disengage, Dodge, Help, Hide, Ready, Search, and Use an Object. The Attack action allows a single melee or ranged attack by default; the Extra Attack class feature (gained at level 5 by Fighters, Paladins, Rangers, Barbarians, and Monks) increases that to 2 attacks per Attack action. Fighters gain a third attack at level 11 and a fourth at level 20.

Attack Resolution

An attack roll adds the d20 result to the attacker's relevant ability modifier plus proficiency bonus (if proficient with the weapon or spell). This total is compared against the target's Armor Class. A natural 20 always hits and produces a critical hit (doubling the number of damage dice rolled); a natural 1 always misses. The advantage and disadvantage system replaces stacking numerical modifiers with a binary mechanic: roll 2d20 and take the higher (advantage) or lower (disadvantage) result. Advantage and disadvantage do not stack with themselves.

Movement and Positioning

Movement and positioning operate on a grid or theater-of-mind basis. The standard grid uses 5-foot squares. Moving through difficult terrain costs 2 feet of movement per 1 foot traversed. Opportunity attacks — a reaction-based melee attack — trigger when a creature leaves an enemy's reach without taking the Disengage action.

Flanking and cover represent optional and core positional mechanics, respectively. Cover grants AC bonuses: half cover provides +2 AC, three-quarters cover provides +5 AC, and total cover prevents targeting entirely. Flanking (an optional rule from the Dungeon Master's Guide, p. 251) grants advantage on melee attacks when two allies are on opposite sides of a target.

Spellcasting in Combat

Spellcasting interacts with the action economy through casting time classifications. A spell with a casting time of 1 action consumes the caster's action. Bonus action spells (such as Healing Word or Misty Step) impose a restriction: if a bonus action spell is cast, the only other spell castable that turn must be a cantrip with a casting time of 1 action. Concentration limits a caster to maintaining one concentration spell at a time, with Constitution saving throws required upon taking damage (DC equals 10 or half the damage taken, whichever is higher).

Causal Relationships or Drivers

Combat outcomes are driven by the intersection of three primary causal chains:

Ability scores and class features as input variables. Ability scores and modifiers determine attack bonuses, damage output, saving throw DCs, and defensive capacity. A Fighter with 20 Strength adds +5 to melee attack and damage rolls before proficiency; a Wizard with 20 Intelligence sets spell save DCs at 8 + proficiency bonus + 5. The character class determines hit die size (d6 for Wizards through d12 for Barbarians), armor and weapon proficiencies, and class-specific combat features.

Equipment as a damage multiplier. The equipment and weapons rules and armor rules set baseline damage dice and AC floors. A greatsword deals 2d6 slashing damage per hit; plate armor provides a base AC of 18. Magic items — particularly +1/+2/+3 weapons and armor — shift these baselines and can break bounded accuracy thresholds.

Resource depletion across encounters. The spell slots and spell levels system creates an attrition pressure: a 5th-level Wizard has 9 total spell slots (4 first-level, 3 second-level, 2 third-level). Spell slots recover on long rests. The resting rules therefore function as a reset mechanism that paces combat difficulty across an adventuring day. The Dungeon Master's Guide (p. 84) assumes 6–8 Medium or Hard encounters per long rest as the design baseline, a figure that directly shapes encounter building.

Classification Boundaries

Combat rules interface with but remain distinct from adjacent subsystems:

Environmental hazards (traps and hazards), poison and disease, and darkness and vision conditions all modify combat resolution without being combat rules per se. Mounted combat and underwater combat each impose variant movement and attack restrictions within the combat framework.

Tradeoffs and Tensions

Action economy versus narrative freedom. The rigid structure of 1 action / 1 bonus action / 1 reaction per turn creates predictable balance but constrains creative actions. Attempting something not listed (swinging from a chandelier, throwing sand in an enemy's eyes) requires Dungeon Master adjudication, often through improvised action rulings.

Bounded accuracy versus character progression. 5e's bounded accuracy system keeps AC and attack bonuses within a narrow numerical band (+4 to +11 for most play). This ensures low-level monsters remain marginally threatening at high levels but creates tension with player expectations of power growth. Backgrounds and feats and subclass features add qualitative versatility rather than raw numerical escalation.

Grid precision versus theater-of-mind speed. Grid combat enables precise positioning, area-of-effect targeting, and opportunity attack tracking. Theater-of-mind combat reduces bookkeeping but introduces ambiguity around distances and spatial relationships.

Short rest versus long rest class balance. Fighters and Warlocks recover key resources on short rests (1 hour); Wizards and Clerics require long rests (8 hours). Encounter density per day disproportionately affects long-rest classes; a single-encounter adventuring day heavily favors spellcasters who can expend all resources in one fight.

Rule-as-written versus rule-as-intended. The 5e D&D core rules rely on natural language rather than keywords, producing interpretive disputes. The optional and variant rules and the 2024 revised rules address certain ambiguities but introduce new classification questions across editions.

Common Misconceptions

"A bonus action is a second action." Bonus actions are mechanically distinct from actions. A creature cannot substitute an action for a bonus action or vice versa. Bonus actions are available only when a specific feature, spell, or ability grants one; without such a grant, a creature has no bonus action to take on a given turn.

"Natural 20 on ability checks automatically succeeds." Under 5e rules as written (Player's Handbook, p. 7, 2014), natural 20s guarantee success only on attack rolls, not ability checks or saving throws. The 2024 revised Player's Handbook extends critical success/failure to ability checks and saving throws — a significant rules change.

"Opportunity attacks trigger whenever an enemy moves." Opportunity attacks trigger only when a creature leaves another creature's reach — not when moving within that reach. A creature with 5-foot reach provokes opportunity attacks only when an enemy moves from 5 feet to 10 feet away.

"Healing in combat is always efficient." At mid-to-high levels (8+), in-combat healing rarely exceeds incoming damage per round. A 3rd-level Cure Wounds heals 3d8 + modifier (average ~17 HP) against monsters dealing 20–40+ damage per round. Healing is most efficient when used to restore a creature from 0 HP to consciousness, leveraging the binary alive/unconscious threshold rather than HP totals.

"Surprise is a full round of free attacks." Surprise is a condition applied to individual creatures, not an entire round. A surprised creature cannot move or take actions on its first turn and cannot take reactions until that turn ends. Unsurprised creatures in the same initiative order act normally.

Checklist or Steps (Non-Advisory)

The following sequence reflects the procedural order of combat resolution as described in the 5e Player's Handbook (Chapter 9):

1. Determine surprise — the DM compares Dexterity (Stealth) checks of hiding creatures against the passive Wisdom (Perception) of targets
2. Establish positions — the DM describes the environment; miniatures or tokens are placed if using a grid
3. Roll initiative — each creature rolls 1d20 + Dexterity modifier; the DM ranks results from highest to lowest to set turn order (initiative and turn order)
4. Take turns — in initiative order, each creature takes its turn: movement, action, bonus action (if available), free object interaction
5. Resolve attacks — the attacking creature rolls 1d20 + attack modifier vs. target AC; hits trigger damage rolls per weapon or spell specifications
6. Apply damage — subtract damage from the target's current HP; if HP reaches 0, the creature falls unconscious (for player characters) or dies (for most monsters)
7. Track conditions — apply and remove conditions as triggered by spells, features, or environmental effects
8. Check concentration — if a concentrating creature takes damage, it makes a Constitution saving throw to maintain the spell
9. Resolve death saves — creatures at 0 HP make death saving throws at the start of each turn (3 successes stabilize; 3 failures result in death) per death and dying rules
10. End combat — combat concludes when one side is eliminated, surrenders, or flees; the DM distributes XP or triggers milestone advancement as applicable

Reference Table or Matrix

For the full index of rule topics, see the site reference index. Additional context on how tabletop recreation activities like D&D relate to structured play frameworks is available in the recreation overview. The D&D as recreation reference provides background on the broader context of tabletop roleplaying within recreational service categories.

References

• [Dungeons & Dragons 5th Edition Player's Handbook (2014)](https://dnd