Game Design

Core Mechanics: Rounds, Turns, and Phases

Most role-playing games that I’ve played use a similar structure for taking turns in combat. At the beginning of a fight, each character makes an initiative roll to determine what order they act in. Then each character takes turns with a character completing most of their actions on their turn then sitting idle as other characters take their turns.

  1. Roll initiative
  2. Characters act in initiative order taking their actions in any order on their turn
  3. Repeat step 2 until end of combat

I think that round structure offers some nice benefits. First, its relatively simple. When its your turn, your character takes whatever actions it can and then you’re done until your next turn. Another benefit is that players generally don’t have to worry about the order of their actions. For example, on your turn, you can move then attack or attack then move.

One problem with the structure is that it introduces a lot of downtime for players while they wait between their turns unable to act. Some games, notably the most recent versions of D&D, have attempted to address this problem by adding a variety of actions that a character can take to interrupt or react to the actions another character takes on its turn.

  1. Roll initiative
  2. Characters act in initiative order
    1. Take their actions in any order on their turn
    2. Other characters can interrupt or react if certain triggers are met
  3. Repeat step 2 until the end of combat

These options help to keep players engaged in combat when it is not their turn and add to a feeling of simultaneity, but they also tend to increase the complexity of combat. For example, immediate interrupts and reactions are often cited as something that bogs down combat in D&D 4E.

Dungeons & Dragons Basic

In the D&D Basic Set (the Moldvay set from 1981), the combat sequence is much different from later editions. Each side rolls initiative rather than individual characters, and initiative is rolled every round rather than only once per combat. Then on a side’s turn, actions happen in a particular order across all of the characters on that side.

  1. Roll initiative
  2. The sides act in initiative order, completing their actions in a set order
    1. Movement
    2. Missile attacks
    3. Magic spells
    4. Melee attacks
  3. Repeat from step 1 until combat ends

While side-based turns are probably simpler than character-based turns, the set order of actions for a turn requires a bit more thinking. For example, since everyone on a side moves at the same time, there is no chance for a party’s wizard to fireball the enemies before the fighter charges into combat later in the same round. In order to pull that off, the fighter would have to decide to stay back and wait for the next round to charge.

The basic rules do contain an optional rule for per-character initiative, but the action order is still maintained when using that rule.

Advanced Dungeons & Dragons Second Edition

AD&D 2E also uses side-based initiative by default, but it drops the fixed order of actions for a side. Instead it requires the DM and players to declare their actions at the beginning of each round before initiative for that round is rolled or any actions are resolved. This twist means that players can declare an action for their character that ends up not making sense by the time their character actually acts.

AD&D 2E also has an early mechanic similar to opportunity attacks where an opponent in melee can make a free attack against a character that retreats by moving more than 1/3 its movement. Because there is only a single simple trigger, this doesn’t seem like it would slow down combat as much as the more open system of opportunity immediate actions seen in 4E.

  1. DM secretly decides what monsters will do
  2. Players declare what their characters will do
  3. Roll initiative
  4. Actions are resolved in initiative order
    1. Opponents may make a free attack if a character retreats from melee
  5. Repeat from step 1 until combat ends

Like D&D Basic, AD&D 2E includes optional rules to replace side-based initiative. The first, known as group initiative, keeps one roll per side but applies per-character modifiers that can stagger when each character’s actions are resolved. For instance, a character using a dagger gets a bonus compared to a character using a greatsword or casting a spell. The second optional rule is individual initiative where each character gets a separate roll with modifiers rather than sharing a single roll.

Warhammer 40,000

Yes, Warhammer 40k is a miniatures war game and not a role-playing game, but its still useful to look at war games for combat mechanics since combat encounters are essentially a skirmish war game embedded in role-playing games.

The Warhammer 40k turn structure is very similar to what Basic D&D uses. The two sides roll to determine who goes first at the beginning of a combat and then take turns acting with a fixed order of actions.

  1. Roll to determine who goes first
  2. The sides act in order, completing their actions in phases
    1. Movement
    2. Shooting
    3. Assault
  3. Repeat step 2 until the end of combat

One important difference from Basic D&D is that during a side’s assault phase, every character involved in melee is able to make attacks. The attacks are resolved in order based on the initiative scores of the characters meaning that even though your unit charges they could take attacks before getting to make any.

Move, Shoot, Assault with a Twist

One thing that Warhammer 40k’s turn structure encourages is fast-closing assault units such as troops with jump packs, cavalry, and beasts. Because these units can combine running movement and a charge into assault in a single turn, they are able to cover something like 18-24″ between opportunities for their opponents to fire weapons. Because most infantry weapons have a maximum range of 24″ and an ideal range of 12″, this means that these assault units can sometimes entirely avoid being shot at by their opponents as they close into melee.

As a potential remedy for that problem I’ve been brainstorming an alternate turn structure that swaps out the active player’s shooting phase for the non-active player’s shooting phase. This would mean that a unit would almost always get an opportunity to fire at a unit charging them at relatively short range. A change like that would shift the balance of the game away from assault forces by making a charge more risky and help out armies that rely on shooting. It would also help address downtime by reducing the amount of time a player is waiting for their opponent’s turn to end.


BattleTech is another wargame, but it uses a turn structure completely different from Warhammer 40k. Instead of each player getting a turn during each round when they take all of their actions, each round is divided into phases with both sides acting during each phase. This means that everyone involved in the combat moves first, then once everyone is done moving, they all make attacks.

  1. Roll initiative
  2. Players take turns moving one unit at a time
  3. Players take turns declaring weapon attacks
  4. Weapons attacks are resolved
  5. Players take turns declaring physical attacks
  6. Physical attacks are resolved
  7. Repeat from step 1 until the end of combat

This turn structure is meant to represent both sides taking their actions simultaneously. One interesting aspect is that the side that wins initiative acts second during each phase. Because resolution happens separately from action declaration, this is actually an advantage because the winner knows what his or her opponent is doing and can react accordingly. For example, the player that lost initiative might move their ‘mech to a position so that they have a clear line-of-sight to the back of their opponent’s ‘mech only to have the player who won initiative later jump jet behind cover.

I personally like this system, and I’ve designed Sword of Terra to use a similar turn structure.

So… Which is Best?

I don’t really think any turn structure can be singled out as the best option. For a fast-paced, simple game, a more basic turn structure without the option to interrupt or react during the turns of other players is going to work best. On the other hand, a more complex turn structure, like what BattleTech uses, can force players to think tactically and work really well for the game meant to emphasize maneuvering and planning ahead.

Have you played any role-playing or war games with turn structures unlike anything I’ve mentioned? What do you like or dislike about the turn structure used by the games you’ve played?

By Scott Boehmer

A game enthusiast and software engineer.

3 replies on “Core Mechanics: Rounds, Turns, and Phases”

My favorite initiative system is from 7th Sea:

Each character rolls a number of d10’s equal to his Panache (rated from 1 to 5).
The GM starts the round on phase 1. Anyone who has a die showing 1 can act during that phase. If you have multiple dice showing 1, you can take multiple actions. Once you take an action, you discard that action die.
The count increments to 2, and players with a die showing 2 can act.
Et cetera.
After phase 10, you go to a new round, and all characters roll a new set of action dice.

If two characters both have actions during the same phase, the character with the highest total of all action dice showing gets to go first. So, while someone with a 2 and two 9s mostly goes later in the round, he is nearly guaranteed to go first on phase 2.

A character can choose to hold her action, saving the action die. She can choose to immediately use her action on any later phase. This is most commonly used for “Active Defense” (e.g., parrying).

If a character needs to perform an action on a phase in which she does not have an action die showing, she may spend two of her later action dice to interrupt the action.

The fact that it uses the tactile dice makes it very easy to track. The really random nature of when you get to go enhances the chaotic feel of combat, and intersperses character turns. That the number of actions you get is based on, essentially, your charisma is so fantastic for a swashbuckling game.

That sounds like a pretty neat system. Did it result in a lot of players favoring high Panache scores or did the game do a pretty good job balancing out other stats so that fewer but better actions was a viable choice?

It did have a lot of players favoring Panache. But, as it’s a swashbuckling game, that was a good thing. The system actually did a pretty amazing job of making every stat count in combat. Panache determined how often you could try to hit, Finesse determined if you could hit, Brawn determined how hard you hit, Wits determined if you could avoid being hit, and Resolve determined if you could take a hit. With a few other system elements, it strongly encouraged building balanced characters.

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