Introduction -- Definitions: tactics, operations, strategy -- Factors and constants: space, time, and forces -- The beginnings: planning, mobility, and a system of expedients -- The sword of Damocles: a two-front war -- Bitter awakening: World War I -- Old wine in new wineskins: operational thinking in the Reichswehr and the Wehrmacht between reality and utopia -- Lost victories, or the limits of operational thinking -- Operational thinking in the age of the atom -- Conclusion.