Warfighting: Nature of War

Friction.  

Countless factors make war difficult to conduct. When the simple is difficult, and the difficult is impossible, we have friction. Friction can be mental or physical. It can come from enemy actions, terrain and whether, or be self-imposed. War is a human endeavor. Friction has a psychological effect. The main weapon against friction is the human will. Training and experience will teach us how to fight in an environment of friction.