To play a game of Warhammer 40,000, you must first select a mission. The mission will tell you how to muster your armies, create your battlefield and deploy your forces on the tabletop. It will also tell you any special rules that apply to the battle, and (most importantly!) what you need to do to win. You can find out more about missions in the Mission section.

Each player in a game of Warhammer 40,000 commands an army of Citadel miniatures, hereafter referred to as models. The mission you have selected will guide you as to how big your army should be.

Models move and fight in units. A unit can have one or more models from a single datasheet (see below). Models and units from the same army are said to be friendly in relation to each other. Models and units from your opponent’s army are referred to as enemy models and units. If a rule affects ‘models’ or ‘units’ without specifying that they are friendly or enemy, that rule affects all models or all units, regardless of whose army they are in.

The rules you will need to use your models in games are presented on datasheets. Each unit has a datasheet; you will need the datasheets for all the units from your army. You can find out more about datasheets in the Datasheet section.

All datasheets have a list of keywords, separated into Faction keywords and other keywords. Faction keywords can be used to help you decide which models to include in your army, but otherwise both sets of keywords are functionally the same. In either case, keywords appear in KEYWORD BOLD. Keywords are sometimes linked to (or ‘tagged’ by) a rule. For example, a rule might say that it applies to INFANTRY units. This means it only applies to units that have the INFANTRY keyword on their datasheet. The pluralisation (or otherwise) of keywords does not affect which units the rule in question applies to.

A unit that contains more than one model must be set up and end any kind of move as a single group, with all of its models within 2" horizontally and 5" vertically of at least one other model from that unit. While a unit has seven or more models, all of its models must instead be set up and end any kind of move within 2" horizontally and 5" vertically of at least two other models from that unit. This is called Unit Coherency.

If for any reason a model cannot be set up in Unit Coherency, or cannot be set up following any restrictions stated by other rules (e.g. while setting up using the Deep Strike ability), that unit cannot be set up. If a unit cannot end a move in Unit Coherency, it cannot make that move and its models are returned to their previous positions.

At the end of every turn, each player must remove models, one at a time, from any of the units from their armies that are no longer in Unit Coherency, until only a single group of models from each of those units remains in play and in Unit Coherency. Models removed in this way count as having been destroyed, but they never trigger any rules that apply when a model is destroyed.

Rules that allow players to redeploy certain units after both armies are deployed (e.g. Huron Blackheart’s Red Corsairs ability) are always resolved after the Deploy Armies step (or, if you are playing a Crusade battle, after the Deploy Crusade Armies step), and before the Determine First Turn step, before determining who has the first turn. When a player uses such a rule, they remove that unit or units from the battlefield, then deploy them again using all the normal rules (for example, if all the models in one of these units have the Infiltrators ability, that unit’s player can set that unit up using that ability). Players alternate resolving any such rules, starting with the Attacker.

Engagement Range represents the zone of threat that models present to their enemies. While a model is within 1" horizontally and 5" vertically of an enemy model, those models – and their units – are within Engagement Range of each other.

Models cannot be set up or end a Normal, Advance or Fall Back move within Engagement Range of any enemy models. If for any reason a model cannot meet this condition, that model is destroyed.

Battles of Warhammer 40,000 are fought on rectangular battlefields. This can be any surface upon which the models can stand – a dining table, for example, or the floor. Your mission will guide you as to the size of battlefield required.

The scenery on a battlefield can be represented by models from the Warhammer 40,000 range. These models are called terrain features to differentiate them from the models that make up an army. Terrain features are set up on the battlefield before the battle begins. You can find out more about terrain features in the Terrain Features section.

Unless the mission you are playing instructs you otherwise, you should feel free to create an exciting battlefield using any terrain features from your collection.

Distances in Warhammer 40,000 are measured in inches ("). You can measure distances whenever you wish.

When measuring the distance between models, measure between the closest points of the bases of the models you’re measuring to and from. If a model does not have a base, measure to the closest point of any part of that model instead.

If a rule says it applies ‘within’ a certain distance, it applies at any distance that is not more than the specified distance. For example, within 1" means any distance that is not more than 1" away.

Warhammer 40,000 uses true line of sight to determine visibility between models. To check this, get a ‘model’s perspective’ view by looking from behind the observing model. For the purposes of determining visibility, an observing model can see through other models in its unit, and a model’s base is also part of that model.

If any part of another model can be seen from any part of the observing model, that other model is visible to the observing model.

If one or more models in a unit is visible to the observing model, then that model’s unit is visible to the observing model.

If every part of another model that is facing the observing model can be seen from any part of the observing model, then that other model is said to be fully visible to the observing model, i.e. the observing model has line of sight to all parts of the other model that are facing it, without any other models or terrain features blocking visibility to any of those parts.

If every model in a unit is fully visible to an observing model, then that unit is fully visible to that observing model. For the purposes of determining if an enemy unit is fully visible, an observing model can see through other models in the unit it is observing.

In order to fight a battle, you will require some six-sided dice (often abbreviated to D6). Some rules refer to 2D6, 3D6 and so on – in such cases, roll that many D6 and add the results together.

If a rule requires you to roll a D3, roll a D6 and halve the result (rounding up to a whole number) to get the D3 result, as shown below.

If a rule requires a dice roll of, for example, 3 or more, this is often abbreviated to 3+. Where several consecutive dice results are relevant to a rule, these are often shown as a range (e.g. 1-3).

Some rules allow you to re-roll a dice roll, which means you get to roll some or all of the dice again. If a rule allows you to re-roll a dice roll that was made by adding several dice together (e.g. 2D6, 3D6, etc.) then, unless otherwise stated, you must re-roll all of those dice again.

You can never re-roll a dice more than once, and re-rolls happen before modifiers (if any) are applied. Rules that refer to the value of an ‘unmodified’ dice roll are referring to the dice result after any re-rolls, but before any modifiers are applied.

Some rules instruct players to roll off. To do so, both players roll one D6, and whoever scores highest wins the roll-off. If there is a tie for the highest roll, roll off again. Neither player is allowed to re-roll or modify any of the D6 when making a roll-off.

While playing Warhammer 40,000, you’ll occasionally find that two or more rules are to be resolved at the same time. If this occurs during the battle, the player whose turn it is chooses the order. If this occurs before or after the battle, or at the start or end of a battle round, the players roll off and the winner decides the order in which those rules are resolved.