->''You glance through the mist obscuring the battlefield (there always seems to be mist on a battlefield -- some say it's to obscure the [[LeaningOnTheFourthWall parts that haven't finished loading yet]], but you don't know what that means).''
->-- ''KingdomOfLoathing''

The expression, not to be confused with the 2003 war documentary about Robert S. [=MacNamara=], ''Film/TheFogOfWar''.

A feature of many [[StrategyGame strategy games]] that keeps the player from seeing everything that happens on the game map by limiting his knowledge of "enemy" units and movements to those areas where he has (or has recently had) units of his own. Some games enhance the effect by having a "partial" fog over areas that the player's explored at least once, but without any units in range at the time to observe.

While this is a realistic limitation, many players find it irritating and restrictive, often because the AI driving the other side [[TheComputerIsACheatingBastard is usually not likewise handicapped]]. Turning off the FogOfWar is thus one of the more popular {{Cheat Code}}s a game could have, or for that matter it can easily be an option to turn it off without any kind of cheat code.

This exists in RealLife, in the sense that you need to have someone or some sensor observing the enemy in order to actually know their whereabouts. However, generally when someone talks about the FogOfWar they mean the sense of confusion created in one's mind when subjected to the chaos of combat. Usually they're talking about commanders making or trying to make decisions while sorting through the morass of time -- late, conflicting, and rushed reports with limited time in which to act. The stress of getting shot at doesn't help. To quote an old saying: "Order, counter-order, disorder."

A SubTrope of WeatherOfWar, see also DefogOfWar on abilities and items that help lessen this.
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!!Examples:
* A RealLife example and possible TropeNamer: [[http://en.wikipedia.org/wiki/Carl_von_Clausewitz Carl von Clausewitz]], wrote in ''On War'' "The great uncertainty of all data in war is a peculiar difficulty, because all action must, to a certain extent, be planned in a mere twilight, which in addition not infrequently ? like the effect of a fog or moonshine -- gives to things exaggerated dimensions and unnatural appearance."
** Clausewitz was referring to both a proverbial and literal fog, the first due to the complex logistics of processing and gathering intelligence, which takes enough time to spoil the freshness of the data, and the second being the amount of dust kicked up by artillery, moving thousand-troop battalions and barrages of black-powder firearms. Contemporary technology has vastly reduced the proverbial fog and plays with (sometimes even invokes) the literal one.
* The various ''VideoGame/{{Warcraft}}'' games and their relatives, like ''VideoGame/{{Starcraft}}'', except the original ''Warcraft.''
** The first ''Warcraft'' had shroud, but no fog while the second had a simple option to turn it off; Starcraft was the first to consider disabling it cheating.
*** ''VideoGame/WarcraftIII'', however, has an option to make the whole map visible from the start. There's still a cheat code to lift it though ([[TheSixthSense iseedeadpeople]]).
** StarcraftII gave the Terrans the Sensor Tower, which causes enemy units to show up as blips in the fog of war, without revealing what they are. It shows up as a honking big circle on everyone's minimap though.
* Anime illustration: In an episode of ''[[SuzumiyaHaruhi The Melancholy Of Haruhi Suzumiya]]'', the SOS-dan was challenged to a computer game with this limitation. Yuki quickly figures out that the opposing side has cheated by removing the Fog Of War on their side, hacks the system, and levels the playing field.
* The turn-based ''VideoGame/{{Civilization}}'' games (including kissing cousin ''SidMeiersAlphaCentauri'') use a Fog of War; one of the diplomatic options available is trading your explored map knowledge with other cultures.
** One particularly realistic aspect of ''Civilization IV'''s FogOfWar is that, though most of your units are removed from an enemy's territory when you declare war, submarines are not. This makes subs the best passive scouts in the game.
*** That's not in the earlier games because ''no'' units were removed from enemy territory upon declaration of war. The rule was introduced in [=Civ IV=] in order to nerf abusive forms of surprise attack (eg. deploying an army next to the to-be-enemy's capital, declaring war, and immediately capturing the city before reinforcements have even a theoretical chance to arrive). Since you generally needed a "Right of Passage" agreement with the other civilization to be able to pull off this trick--crossing another civilization's territory without such an agreement would cause ''them'' to declare war on ''you'' before you got anywhere near the capital--this had the charming nickname "[=RoP=] Rape".[[note]]On the other hand, if you ''could'' get your troops to the target civ's capital or other desired territory before they declared war on you without needing an [=RoP=], engineering a PretextForWar that the AI civs would be too dumb to realize was your fault not theirs was child's play, [[WoundedGazelleGambit allowing you to be as aggressive as you liked without ever suffering a trustworthiness penalty]]. This was especially deadly when you had a Mutual Defense treaty with the third civ: get mutual defense with your desired enemy's neighbor; "peacefully" violate "enemy" territory; wait for them to declare war; and have yourself a war with an enemy fighting on two fronts. And [[UsefulNotes/WorldWarI we all know what]] [[UsefulNotes/WorldWarII happens when you fight on two fronts]]...[[/note]]
*** Then again, the description for subs states rather explicitly that they can explore rival territory and are hidden from most units. What else would you expect?
---> '''Opponent:''' Remove your submarines, whose whereabouts are unknown to me, from my territory!
---> '''You:''' Er ... ok, done!
** Also, in Civ-series games, launching your first satellite will remove the Fog of War once and for all. Spysats rule!
*** In Civ4, they only do this once (when you discover the Satellite technology), but not for all.
** Additionally, if you founded a religion and that religion is in a city, you can see that city and the immediate area, the same is true as you increase your spy points with a civ. You can even steal the location of all military units, though it is only good from that turn.
*** This system was reworked for the ''Beyond the Sword'' expansion - owning the religion's holy city (where it was founded) no longer entitles you to automatic line of sight of a rival city with that religion. Rather, espionage now has its own points system (among them, accumulating a certain amount of points entitles you to look at known rival cities).
* Original DawnOfWar made heavy use of the this, even detailing it by this name in the tutorial.
* DarkReign was one of the first games to use complex fog of war, making it possible to set ambushes by hiding below cliffs, in depressions in the ground, behind hills, etc.
* Certain levels in the strategy-card game ''VideoGame/MetalGearAcid'' and its sequel were in 'Search Mode', which allowed you to see terrain and items but not enemies -- until you were standing very close to them. Thankfully, there are multiple cards which extend your range of eyesight. Not so thankfully, getting hit by an enemy in Search Mode renders you completely blind for some reason we can only guess at. While the effect wears off in a set number of turns, you have few ways of fighting back and no idea where to run from to hide, turning you into a sitting duck. The good news is that it completely subverts TheComputerIsACheatingBastard-type AI; you play in FogOfWar-mode for only a handful of levels. The computer plays in it ''all the time''.
* PC example: ''{{DEFCON}}: Everybody Dies'' only allows you to see enemy units that enter within range of your and your allies' radar. You cannot tell where the enemy's defensive units are unless you send some offensive units within radar range -- which allows both sides to see each other.
* The AdvanceWars games featured Fog of War, but only on certain maps or settings. This fog actually affects AI, since it will ignore units that are hidden in forests or reefs by the fog ([[TheComputerIsACheatingBastard except in the first two games]]). Recon units have extra vision radius, infantry and mechs get an extra square if [[IHaveTheHighGround they're on mountains]], and in ''Dual Strike'', Sonja gives all her units extra vision.
** The games also have (optional) weather conditions. Rain usually limits the vision further and even adds temporary FogOfWar if not present on the battlefield.
** In a slight twist, the characters talk about it like a physical object and think it's perfectly natural for you to see the entire map one battle and have fog of war the next.
** Completely [[JustifiedTrope justified]] in ''Days of Ruin'', where it is present as dust kicked up from the meteoric impact which destroyed most of civilization.
** The AI actually handles fog of war differently in each game:
*** In the GBA Advance Wars titles, the AI had full knowledge of your units, and could attack unhindered; the only way to protect yourself is to hide in forests and reefs, where the AI cannot fire unless they have an adjacent unit (or if Sonja has her COP active).
*** In AW:DS, the AI will maneuver as if omniscient, but has to station a unit to reveal yours before attacking.
*** In Days of Ruin/Dark Conflict, the AI behaves as though fully affected by FoW.
** Also, interestingly enough, in Days of Ruin/Dark Conflict, the paths any of your units travel, as well as the spaces directly adjacent to the paths, are revealed until the end of your turn. It's a real cheap way to scope out numerous forests at once (but keep in mind the AI can do it as well).
* The ''FireEmblem'' series, starting with ''Thracia 776'', has maps with fog. It can be literal fog, nighttime darkness, or in some cases other weather effects (up to blizzards and sandstorms), but it functions with the same fog-of-war rules as ''Advance Wars'', sans units being able to hide on certain terrain. In some of the games, Thieves get to see much farther in the fog.
** [[MyRulesAreNotYourRules Enemies will have no trouble hunting you down in that darkness, though.]]
* The ''VideoGame/{{Homeworld}}'' series features three dimensional fog of war, with special units such as Recon ships and Sensor Arrays that extend the range your ships can detect, or even lift the fog of war for your side completely. These units are a prime target for human opponents.
* ''{{Achron}}'' has an interesting variation, because the fog only blocks vision of units. You can still hear units in the fog, and you can see crates and particle effects from weapons. This is explained that the units are actually camouflaged so they can only be seen at short distance.
* The PC game ''People's General'' includes a sort of fog of war, where you can see the whole map, but no units except those within sight of your own. Depending on how well you can see them, you will either fully identify a unit, or simply see that there is an enemy unit there but not what type. Since running into an unseen unit leads to devastating ambushes, and since Recon units can help conceal other units, making sure you know where the enemy is is a major part of your strategy.
** This is also the case in the ''VideoGame/PanzerGeneral'' games, which are part of the same franchise.
* ''{{Harpoon}}'', has realistic FogOfWar, which is to say knowledge of (for example) [[http://en.wikipedia.org/wiki/Brevity_code#B bandits]] (or [[http://en.wikipedia.org/wiki/Brevity_code#B bogeys]]) is limited by how they are detected; a contact ping on radar may just give distance, bearing and heading. A visual sighting might be necessary to determine its nationality and intent. [[labelnote:more...]]Being a tactical naval simulator, ''Harpoon'' borrows a lot of features from traditional simulations (like the [[http://en.wikipedia.org/wiki/Silent_Hunter Silent Hunter]] series of submarine games), including 1:1 time scale, and handling each sensor contact individually.[[/labelnote]]
* The definitive feature of the Japan only Game Boy Color game ''Kakurenbo Battle Monster Tactics'', which is expected when you realize that the term "kakurenbo" means "hide and seek." Only the first battle DOESN'T use fog.
* Its inclusion in Force Commander, a ''Franchise/StarWars'' RTS, was a big sticking point -- among many. Since all units are landed from orbit, it is hard to believe no one thought to take even a single satellite photo of at least the terrain.
** Cloudy weather.
* ''Outpost 2'', which was more of a city-builder with RTS elements and predates a lot of the early examples, didn't have it at all. The player's view was real-time from space, so any activity at the enemy base was totally in-view. The only things that were hidden were enemy units moving at night with their lights off; they were visible, but they wouldn't show up on the MiniMap.
* ''ParaWorld'' quite literally has a FogOfWar-the areas that aren't within sight range of your units are covered in fog, obscuring enemy units and leaving only wild animals and enemy buildings visible. This has the unfortunate effect of slowing the game down, so it's usually more desirable to turn it off.
* in the RTS TotalAnnihilation, most of the fixed base defenses and artillery units can't even see as far as they can fire, so in order for them to operate effectively, you have to set out patrols of scout units around the perimeter to keep the Fog cleared. Fortunately, the game's excellent command interface makes this a piece of cake, no matter how large or convoluted the perimeter.
** Also, in the spiritual successor Supreme Commander, this can be taken to extremes -- the maps being so much bigger, and many of the weapons having realistic range (one experimental unit has a range of over 100 kilometers), it's possible to bombard positions that are right on the other side of the biggest maps, although the best accuracy is achieved when using either radar or spy planes to provide visual targeting information.
*** Both games had Fog of War, where there was no vision from units, but only Total Annihilation had the unexplored shroud.
* In ''VideoGame/{{Fallout 2}}'', your character can moan about the FogOfWar-like effect your [=PipBoy=] demonstrates when you haven't explored an area.
* The CommandAndConquer games (And their [[DuneII Dune-based predecessors]]) include a common building, the ''Outpost'' (or "Command Center") which allows one to see the radar screen, which views everything not in the (unexplored) shroud. [[YouRequireMoreVespeneGas Power requirements]] must be met to keep the outpost working. But this means the fog of war is lifted in all explored areas of the battlefield.
** In C&C ''Generals'', the radar screen only sees enemies in the line of sight of units on the field. It's built into the USA and China command centers and still requires power. The GLA have a special vehicle (and don't contend with power at all).
** Also some of the C&C games give players access to units and structures that can ''create'' fog of war through either radar jamming or large-scale cloaking fields.
*** Which have the unfortunate tendency to backfire by creating conspicuous areas on the map that ''look'' like fog of war but ''move'' like enemy units.
**** Not to mention there is always some sort of equipment that reveals part of or the entire map. If your opponent tried to reveal only a portion of your base, and it gets recovered, he just found out where your base is. If he revealed the entire map (and the [[CommandAndConquerRedAlert Allies]] usually had both the Gap Generator ''and'' the Outpost that revealed the entire map), now he has a giant black dot on his screen broadcasting where he should aim that nuke. To top it off, savvy players can easily pinpoint where the generator is by finding the center of said dot, and aiming in the general area usually means you hit ''something'' important.
***** Allied players however, tend to also place Gap Generators in completely random and pointless locations, leading to wasted nukes.
*** In Red Alert the Allies also had a Radar Jammer, which would temporarily stop the opponent's Radar Dome from working if it got within range. Unsurprisingly its range is pathetically short.
** In Tiberian Sun and its sequel Tiberium Wars, Nod can build stealth generators which are actually usable, since you can effectively hide your units and bases while still letting your opponent explore the area. It's hilariously useless in a game with AI, as the AI will gladly build walls and pavement around it (which are NOT cloaked) and can see invisible units. When you're wandering around a suspiciously well-kept concrete fort, you know where to aim that nuke.
*** Swings back again to pitifully useless in Tiberium Wars, as the generators themselves do not cloak and cannot be cloaked in any way whatsoever. Since everything else is cloaked, the enemy easily knows what to shoot now.
**** That's to [[MindScrew mess with the heads]] of human opponents; make them think there are bases in places where they aren't
* ''Franchise/{{Disgaea}}'''s multiplayer mode has this as an option. No one's quite certain why.
** Because at higher levels, attacks tend to become {{One Hit Kill}}s. Without a fog, players would likely just hang around just outside the enemy's range until the opponent makes a mistake or they start throwing each other around.
* Even ''VideoGame/DwarfFortress'' has a FogOfWar of sorts. Unlike most examples, it's underground.
* [[JustifiedTrope Justified]] in ''Star Wars: EmpireAtWar'' with infantry sight ranges and vehicle sensor (or whatever) ranges. One particularly annoying bug in the expansion ''Forces of Corruption'', at least with the Zann Consortium, is the Fog of War lifting for no explained reason what-so-ever, allowing a player with their faction's space special weapon (Ion Cannon, Hypervelocity Cannon, and Plasma Cannon for Rebellion, Empire, and Consortium, respectively) to blow up enemy ships LONG BEFORE THOSE SHIPS WOULD BE WITHIN SIGHT RANGE.
** It's not a bug, there's a building(satellite in space) that you can capture that reveals the whole map. They're one of the first things players go for aside from resource nodes.
*** It occurs even on maps that don't have those, and usually occurs before the structure gets captured ANYWAY. It also occurs in ground battles.
* NintendoWars has had it since ''Game Boy Wars''.
* The VideoGame/AgeOfEmpires games have the standard Fog, and also include ''Shroud'', representing that you have not explored an area and have no idea of the landscape. Unlike Fog, Shroud remains gone once the area is explored (as you now know the landscape), and will ''not'' come back.
* ''SinsofaSolarEmpire'': Planets and the legal phase jumps between them have to be explored. A ship or building provides intel for the entire gravity well, but planets without a presence will only show your most recent intel. [[strike:The TEC faction]] any factions can also research the ability to detect incoming ships from one or two phase jumps away. Vasari's 8th level tech (super tech) can detect jumps from anywhere in the map.
** The Advent also have Fog-of-War-reducing Culture abilities.
** You can share intel about ships and planets with enemy factions. It goes both ways.
** It's interesting to know what's going on from scout frigates and can be incredibly useful in the early game, but after a certain point any planet's defensive emplacements would rip a scout apart if you weren't microing that sucker. But by that time, you tend to not need much intel, and what you ''do'' need, you can get by pushing into his systems with fleets instead of scouts.
* The TotalWar games suffer from having a fog of war that makes it difficult to learn about major historical events. Apparently Rome would have taken years to find out if Carthage had conquered Egypt, and the English king may have been kept waiting for decades before he found out that the Turks had taken Constantinople and Vienna.
** You are informed about rather more general events however, like which country in the world that you've never encountered in any form has the largest income or army in the world. Even though you don't know where they are.
** Thus the reason for having diplomats. Trading maps helps to keep you up on who has conquered who. Also keeping track of whose at war helps.
** The game also has ''literal'' fog of war, because if your battle takes place in rain or early in the morning, there can be fog that makes it difficult to see your enemy.
* ''JaggedAlliance 2'' has a partial FogOfWar. After exploring a sector on the map, any enemy movement through that sector is quite visible. However, you will not know the strength or size of the enemy group until it comes within range of your militia (or attacks you). This is changed somewhat with much later mods, where enemies may be completely invisible on the map until spotted by a militia unit.
* Most turn-based tactical/squad games require your soldiers to be looking in the correct direction to spot enemies. So any piece of the battlefield that is NOT being watched, regardless of how close to your soldiers it really is, is considered to be "fogged".
* ''VideoGame/{{Commandos}}'' plays the trope in reverse -- only the enemy is affected by fog of war, as they cannot see your commandos unless specifically looking at their direction, while you (the player) can pretty much see the entire map and every enemy in it from the very start of the mission. The whole point is to plan your assault in advance, based on the enemy's repetitive scouting routes.
* The most recently-added Veteran Reward in ''CityOfHeroes'' is a power that allows one to completely remove the Fog of War from any map. However, it has the drawbacks of taking a moment or two for the map to load in instanced missions, and the fact that the fog of war can acually be beneficial in telling which parts of a map have been explored and which haven't.
* Strangely enough, the manga OnePiece has recently begun a war in which mist is constantly seen sneaking on to the screen from no one knows where.
* In ''Master of Orion II'' the planetary systems on the map are all visible from the beginning, but the actual planets in each system cannot be seen until explored. Likewise, ships of other races cannot be seen if they are outside scanner range. The right leader or racial ability will reveal planets and their ownership. Curiously, the color of the stars tell the player what kinds of planets they're likely to have.
* ''VideoGame/FootballManager'' is a non-wargame example. Players you or your scouts do not know about have no visible attributes, and need to be scouted a couple of times to reveal how good they are. After a period of time, the fog descends again and attributes gradually become hidden. Famous players and frequent opponents are always fully visible.
* Done partially in ''OgreBattle'', where you can't see enemies unless they're close to you. How close depends on the angle.
* ''{{X-COM}}'' reveals the terrain as it's explored, but doesn't show which parts are not visible at the moment, while aliens are only visible if they're within your troops' line of sight. After you've explored the entire map, it becomes frustrating trying to find that last alien when you're not even sure where to look. This problem is averted in the [[XComEnemyUnknown reboot]], where after a certain number of turns the enemy will come to you.
* Played straight in the 1992 film of ''Film/LastOfTheMohicans''. Musket fire apparently creates clouds of smoke thick enough to blanket the adjoining lake, and the heroes literally escape through the resulting FogOfWar.
* Bizarrely averted in the ''Film/LordOfTheRings: the Return of the King'', where the lack of dust on the battlefield makes the CGI armies look fake -- a flaw compared to other films around the same time that used CGI doubling to create huge armies.
* In real life, large crowds create huge clouds of dust, especially with horses or vehicles, unless the field is muddy -- in which case armored cavalry will die up when placed against pikes and arrows.
** In addition to dust and fog obscuring vision it is still very difficult to get an accurate assessment of a battlefield even with satellites, radios and observational aircraft due to countermeasures and the inherent chaos of the situation.
* In ''VideoGame/PlantsVsZombies'', you have to deal with it throughout all of World 4, with the fog getting worse with each level. In 4-10, they go all-out and just replace the fog with a BlackoutBasement level.
* Carr Software's ''[[http://www.carrsoft.com/ctf/capture_the_flag_game.html Capture The Flag]]'' allowed for two levels of Fog-of-War. One let you see changes in any sector of the map you have previously seen. Two other only lets you see changes in sections of the map that your active players could see.
* The entire challenge of the [[BoardGames Board Game]] ''TabletopGame/{{Battleship}}''. Neither of you can see your opponent's units, and your opponent is only allowed to inform you, after each shot, whether it hit or missed.
* You can only see what your units see in ''VideoGame/GrimGrimoire'', though you eventually gain a spell called Clairvoyance that allows you to (temporarily) lift the fog of war.
* In the various ''SpaceEmpires'' games, viewing a star system's map only lets you see stars and planets and other stellar bodies. You can't see enemy or neutral units or colonies unless you have a unit or ship of your own in the system.
* In ''VideoGame/GadgetTrial'', all missions have FogOfWar engaged, and there's no option to disable it. The enemy also is completely unaffected by it. This is compensated for by the fact that the enemy is [[ArtificialStupidity really, really stupid]].
* The naval warfare simulator "PT-boats: Knights of the sea" has this on two levels, first there's the range at which ships can detect (and usually engage) enemy units, as shown in the map screen, but in addition there's also literal fog limitting visual contact in the first and third person views available.
* ''GalacticCivilizations'': you can see systems on the map but not precisely where they are until you send a ship there, plus if you don't have a ship in or near a system you'll only be able to see enemy ships that are in orbit around a planet. There's even a tech tree for expanding how far you can see through the interstellar void. Luckily, it also affects the enemy, and one fun tactic is to keep fast-moving troop transports out of a soon-to-be enemy's line of sight, then launch a smash and grab with a massive battlefleet carving through their defenses to open a space for the troopship.
* This is province based in''KnightsOfHonor'', you can see what's happening in the entire province once your marshall crosses the border. Also applies to your spies in enemy courts, depending on what they are employed as.
** If employed as a marshal the same rules apply as for your own marshals.
** If employed as a cleric, builder or landlord the Fog disappears for the specific province they are assigned to.
* At least two chess variants, with sub-variants:
** Kriegsspiel: you donít see your opponentís pieces at all
** Dark chess: you only see those pieces you can attack.
* ''VideoGames/NeptunesPride'' has Fog of War turned off by default, but it can be enabled by turning on Dark Galaxy mode in the game creation options.
* ''VideoGame/KingdomHeartsII'' has a Heartless called the [[IronicName Illuminator]] whose only ability is to create this. The problem? Your fighting Barbossa. He's invincible until you take down the Illuminator, which can respawn.
* ''TabletopGame/AdvancedSquadLeader'' has a mechanic called Concealment. Units can be marked with a "?" marker at the start of the game, which means the opponent is not allowed to look at them. The other counters under this "?" can be good units, bad units or even dummies.
* ''VideoGame/WargameEuropeanEscalation'' and its sequels handle this in probably the most realistic way possible; the entire map is visible from the start, but there is no way to see enemy units unless you have one of your units in a position to observe them. And if your observer doesn't have the right sensors or the competence (represented by an "optics" score), or the enemy is particularly good at hiding (represented by a "stealth" score), you may not even be able to get a good idea of what the unit is, just that it happens to be there. As one might imagine, good recon units are some of the most valuable units available, and a large part of every battle revolves around trying to get your own scouts into good positions while killing every enemy recon unit you can find as soon as possible.
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