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The FoW switch in the Difficulty settings (No Fog of War Icons) only controls the actual in-game map icons associated with the FoW option settings in a particular mission. (For instance, an enemy plane detected by one of your ship's 'radar'. Or, ground units detected by 'recon' planes.)

If the FoW feature(s) was not activated in the mission by the mission builder, the FoW switch will do nothing. So, this switch will not 'activate' any FoW settings.

The same goes for campaigns. The Fog of War Difficulty setting has no effect unless the option is enabled in each individual mission. Even if you opened each mission and enabled the Fog of War setting, it probably would not have much of an effect on the mission itself. This is because the FOW feature is very much a custom setting....meaning that the person building the mission would need to add particular elements to take advantage of the FOW features.

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