Fog of War

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Hiding information about parts of game worlds that are not being observed or have not yet been explored by players.

While many games give players views of game worlds that could not be achieved by any diegetic entity, it in many cases makes sense to limit players' information to that which his or her units could perceive. This juxtaposition between a non-diegetic player's view and the perception possible by diegetic entities is called Fog of War, from the awareness from military leaders that they have to act without full information about the situation.


Fog of War originated in Wargames and is here typically limited to the presence of identity of enemy units. Examples of such games include Advanced Squad Leader, Rommel in the Desert, and Stratego. A futuristic example is Space Hulk.

Computer-based Strategy Games can introduce a second level, hiding the game world until explored, since computers can easily handle the added excise. Games that make use of this include the Advance Wars, Age of Empire, Civilization, Europa Universalis, and the Hearts of Iron series but it should be noted that Carcassonne, Dominant Species, Drakborgen, and Zombies!!! show that Board Games can also support this type of Fog of War. For the Civilization series, players start with just the areas around his or her starting units explored and the choice between whether to put resources into improving ones cities or exploring the environment can make the difference between success and failure in the game. In later installments of the game, some units can be given upgrades that improve their range and thereby lessen the Fog of War.

Metroid Fusion reveals most of the layout of each level and even explicitly indicates the places the player has already visited. The game further indicates the location of the power-ups on the overview map, but not the exact location on the play area. The in-game tactical maps in the Battlefield series show all terrain features, friendly units, and all enemy units spotted by any friendly units.

The GiantBomb web site has a page for Fog of War listing numerous examples[1].

Using the pattern

Fog of War is used to hide information about Game Worlds, and in addition hide information in Mini-maps for games that use these. Two main design choices exist for Fog of War: how is it dispersed and is it divided into a Fog of War concerning terrain and a Fog of War concerning Units. The former is mainly a question of if terrain should be visible from the beginning of game instances or should be revealed the first time the Fog of War is dispersed for an area. A third alternative is if the game should show the presence of Resources or if these should be hidden; this creates Secret Resources and can be considered independently of if a Fog of War hides the terrain or enemy units (diegetic explanations might be that Resources need to be prospected or that Units can hide).

Fog of War is typically removed for all parts of Game Worlds in the observational ranges of Avatars or Units, and restored when these game elements have moved away or been removed from gameplay. The observational ranges are in this sense Line of Sight functions with a maximum limit. This makes these patterns able to instantiate the pattern even if they functionally remove it during gameplay. Installations can also work as removers of Fog of War, but since these cannot move, their role in relation to the pattern is to let players keep having overview of a location they have taken control over or in which they have built an Installation. Giving these Avatars, Units, and Installations the ability to affect Fog of War opens up possibilities of granting some of these Privileged Abilities in regards to the Fog of War. Some games, e.g. Carcassonne, Drakborgen, and Zombies!!!, have Fog of War simply because their Game Worlds are built during gameplay. For these Tile-Laying can be said to create the Fog of War although it like the previous cases actually removes the Fog of War. This type of Fog of War is however shared between all players.

Interface Aspects

Fog of War is an Information Pattern. In games with Combat, Fog of War allows for Surprise Attacks.


Fog of War modulates players' perception of Game Worlds or Game State Overviews by giving them an Uncertainty of Information. Through this, it provides means of giving Imperfect Information in games with Third-Person or God Views comparable to that which comes automatically in games with First-Person Views. In games where Fog of War is not the same for all players, it gives them Asymmetric Information, and makes it possible for them to have Secret Resources. It can modulate God Fingers so that one has the freedom to move over entire Game Worlds but without revealing all information within them. In games with Reconfigurable Game Worlds, Fog of War can require players to engage in Memorizing.

Since knowing the terrain of Game Worlds, and what the terrains contain, often give tactical advantages, the presence of Fog of War naturally creates Gain Information and, more specifically, Game World Exploration goals. When Fog of War comes in two layers, making a difference between what has not been seen at all and that which currently is not seen, the pattern also modulates Game World Exploration since it encourages players to explore the same areas repeatedly to notice difference. When this becomes a more structure gameplay activity, it is in fact a Guard or Reconnaissance goal. Needing to consider Fog of War in these ways affect how players can and need to do Stimulated and Tactical Planning.

Fog of War can modulate many types of actions through introducing Imperfect Information, but this is probably most directly noticeable in games with Combat.


Can Instantiate

Asymmetric Information, Gain Information, Game World Exploration, Guard, Imperfect Information, Reconnaissance, Secret Resources, Uncertainty of Information

with Combat

Surprise Attacks

with Reconfigurable Game Worlds


with Resources

Secret Resources

Can Modulate

Combat, Game State Overviews, Game World Exploration, Game Worlds, God Fingers, God Views, Mini-maps, Resources, Stimulated Planning, Tactical Planning, Third-Person Views

Can Be Instantiated By

Avatars, Installations, Line of Sight, Tile-Laying, Units

Can Be Modulated By

Privileged Abilities

Possible Closure Effects


Potentially Conflicting With



An updated version of the pattern Fog of War that was part of the original collection in the book Patterns in Game Design[2].


  1. Page on the GiantBomb site for the concept Fog of War.
  2. Björk, S. & Holopainen, J. (2004) Patterns in Game Design. Charles River Media. ISBN1-58450-354-8.