War is an act of violence, which in its application knows no bounds

[Der Krieg ist ein Akt der Gewalt, und es gibt in der Anwendung derselben keine Grenzen.]

Karl von Clausewitz (1780-1831) Prussian soldier, historian, military theorist

On War [Vom Kriege], Book 1, ch. 1 “What Is War? [Was ist der Krieg?],” § 3 (1.1.3) (1832) [tr. Graham (1873)]
    (Source)

(Source (German)). Alternate translations:

War is an act of violence pushed to its utmost bounds.
[tr. Graham/Maude (1908)]

War is an act of force, and to the application of that force there is no limit.
[tr. Jolles (1943)]

War is an act of force, and there is no logical limit to the application of that force.
[tr. Howard & Paret (1976)]