For the documentary, see The Fog of War.

The fog of war is the lack of knowledge that occurs during a war. Most importantly, it refers to each side's uncertainty about the enemy's capabilities and plans, but it also includes the chaos that can occur in one's own forces, for instance when a unit misinterprets its orders, or takes a wrong turn and becomes lost.

Much of the modern military's technological efforts, under the rubric of command and control, seeks to reduce the fog of war, although the 2003 invasion of Iraq demonstrated that even the most advanced technology does not eliminate it; the coalition military conducted the entire operation as if the Iraqi use of WMD could happen at any moment, although later it was found that no such weapons were available to military units.

In video games, particularly real time strategy games, it usually specifically means the ability of enemy units to pass through unoccupied or unexplored sections of the map without being seen, and may be available as a switchable option. For single-player campaigns in games such as the Advance Wars series, specific missions will have fog of war in place. Usually, this means that while the player cannot see distant enemy (computer-controlled) units, the enemy can "see" the player's units perfectly well.

The term is usually ascribed to the Prussian military analyst Karl von Clausewitz, who wrote: "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."

External links

• "The Fog of War: Eleven Lessons from the Life of Robert S. McNamara", an award-winning educational website based on the life of Robert S. McNamara
• Lessons Unlearnt: The Fog of War