Fog of war
The fog of war is the uncertainty in situational awareness experienced by participants in military operations. The term seeks to capture the uncertainty regarding one's own capability, adversary capability, and adversary intent during an engagement, operation, or campaign.
The concept was introduced by the Prussian military analyst Carl von Clausewitz in his posthumously published book, Vom Kriege (1837), which appeared in English translation in 1873 under the title On War:
The nature of the ambiguity described as the fog of war varies according to the level at which participants are engaged.
Grand strategic 
Ambiguity is related to the political intent, capabilities and logistical strengths of an adversary. Sources of information include diplomatic intelligence, secret (or special) intelligence, strategic modeling and data derived from open source intelligence. Affected participants seek to understand intent of and political motivations. Outcomes at this level may encompass military action but are more concerned with socio-political and economic outcomes from which it might cascade if left unattended.
Military strategic 
Militarily, the ambiguity experienced at this level relates to the structure, strength, capability, and disposition of own and adversary offensive and defensive assets. Own-force ambiguity can be caused by failure to report material deficiencies or an unwillingness to escalate concerns, leading to an optimistic view of own capabilities. Adversary ambiguity may be a result of inaccurate intelligence, sources being subverted or deceived, or adversary intelligence presenting a superior picture allowing one's decision cycle to be compromised. In addition, if unanticipated situations occur they can hamper the execution of long term planning.
Within the operational theatre the commander undertakes tasks as directed by the Military Strategic level, ambiguity continues to relate to adversary capability and intent but is coupled with own directive ambiguity, the commander not having the full sight of the strategic imperative. As operational tempo increases at this level the ambiguity experienced by the commander is susceptible to delays in communication of the tactical situation and the ebb and flow of own force, and adversary force interaction. The commander seeks to penetrate the fog of war through significant use of reconnaissance assets and a comprehensive Joint Operational Picture.
Ambiguity stems from several factors at the tactical level, both by deliberate means by the enemy (including active deception and/or electronic attack on communications and sensors) as well as factors inherent to battle resulting in lack of comprehension by commanders as to the tactical environment, the logistic status of their own units, how they are interacting with each other, or their intentions. This lack of comprehension can stem from many factors, individually or in combination, such as poor reconnaissance; inaccurate intelligence; or faulty communication. The tempo of decision making at the tactical level is much greater than at other levels, increasing the risk of escalating ambiguity as assumptions build and resources are allocated based on those assumptions.
The practical experience of the fog of war is most easily demonstrated in the tactical battlespace. It may include military commanders' incomplete or inaccurate intelligence about the enemy's numbers, disposition, capabilities, and intent, regarding features of the battlefield, and incomplete knowledge of the state of their own forces. Fog of war is caused by the limits of reconnaissance, by the enemy's feints and disinformation, by delays in receiving intelligence and difficulties passing orders, and by the difficult task of forming a cogent picture from a very large (or very small) amount of diverse data.
When a force engages in battle and the urgency for good intelligence increases, so does the fog of war and chaos of the battlefield, while military units become preoccupied with fighting or are lost (either destroyed by enemy fire or literally lose their way), reconnaissance and liaison elements become unavailable, the minimum distance for effective communication increases, and sometimes real fog and smoke obscure vision (hence obscuring communication). Much of the modern military's technological efforts, under the rubric of command and control seek to reduce the fog of war. Although even the most advanced technology cannot eliminate it, military theorists continue to develop ways to reduce it.
Simulations and games 
Abstract and military board games sometimes try to capture the effect of the fog of war by hiding the identity of playing pieces, by keeping them face down or turned away from the opposing player (as in Stratego) or covered (as in Squad Leader). Other games, such as the Kriegspiel chess-variant, playing pieces are hidden from the opponent by tracking them on paper or by using a duplicate, hidden game board.
Solitaire games also by their nature attempt to recreate fog of war using random dice rolls, card draws, or flowcharts to determine events, for example Ambush!. Complex double-blind miniatures wargames, including cloth model training exercises for military commanders, may make use of two identical maps or model landscapes, one or more referees providing limited intelligence to the opposing sides, participants in the roles of sub-unit leaders, and the use of radio sets or intercoms.
The term "fog of war" has become jargon in military and adventure video and computer games, in the more limited sense of enemy units or characters being hidden from the player. Often this is done by obscuring sections of the map already explored by the player with a grey fog whenever they do not have a unit in that area to report on what is there. The player can still view the terrain but not any enemy units on it. One early use of fog of war was the 1978 game Tanktics designed by Chris Crawford, which was criticized for its fog of war system detracting from the fun of the game. Crawford later noted that "...when the games get too realistic, they lose their appeal."
Two of the most successful Blizzard franchises, Warcraft and StarCraft, also use a similar fog of war which only reveals terrain features and enemy units through a player's reconnaissance. Without a unit actively observing, previously revealed areas of the map are subject to a shroud through which only terrain is visible, but not changes in enemy units or bases. Total Annihilation and Supreme Commander are two examples where the use of radar is crucial to detecting units within the fog of war. EA Games' Command & Conquer franchise has incorporated a similar fog of war through the series, as has Activision's Dark Reign: The Future of War; the same type of effect is present in EA Games' Genie Engine which powers games including Age of Empires and Star Wars: Galactic Battlegrounds. Similarly, in Classic Empire video game, a player can only observe an enemy unit if it is in the vicinity of one of the player's units or cities. In some games, such as Command & Conquer: Red Alert 2, it is possible for the player to artificially recreate a fog of war against his opponent. In turn-based strategy games of the Advance Wars, Field Commander and Fire Emblem series, "Fog of War" refers to a fog which shrouds the most part of a map. Sid Meier's turn-based franchise Civilization and its spin-off Alpha Centauri obscure parts of the map not occupied by the player or allies until the advent of orbital flight is reached by the player.
By extension, "fog of war" is also used to describe the limited view distance of first-person shooters, where unlimited view is considered either bad for gameplay or, more often, because of technical limitations, in that a fog of war allows for the rendering of a smaller part of the game area. In the Commands & Colors series of boardgames, designed by Richard Borg, the fog of war is simulated by a deck of cards from which the players can pick their actions. Different sides of the battle usually have a different number of cards (each one describing a possible action) and players have to choose which card to use. It often happens that the best action imaginable in that moment is impossible to do because the player does not have a useful card for it. This is to simulate the difficulty of in-battle communication in the heat of the moment.
See also 
- Joint Service Command and Staff College, Advanced Command and Staff Course Notes dated 2001
- Carl von Clausewitz, Vom Kriege, Book 1, Chapter 3.
- Squad Leader Rulebook, 4th Edition, section 25.0.
- ""Fog of War": A Clearer View", Computer Gaming World, April 1988: 24–26, 52–53
Further reading 
- The Fog of War and Friction in Current Conflicts: Fundamental Aspects of the Management of Modern Conflicts Article by LCdr (Brazilian Navy) Osvaldo P. Caninas.