Friction and Fog of War

"Everything in war is simple, but the simplest thing is difficult." This quote by Clausewitz encapsulates the meaning of "friction". The concept refers to minor problems in implementing a battle plan. These issues accumulate, constituting the difference between a plan and its implementation. Related to friction is the problem regarding uncertainty of knowledge. Although Clausewitz himself never mentioned the term, this uncertainty has been referred to as the "fog of war".