The invention of gunpowder and the constant improvement of firearms are enough in themselves to show that the advance of civilization has done nothing practical to alter or deflect the impulse to destroy the enemy, which is central to the very idea of war.

[Die Erfindung des Pulvers, die immer weiter gehende Ausbildung des Feuergewehrs zeigen schon hinreichend, dase die in dem Begriff des Krieges liegende Tendenz zur Vernichtung des Gegners auch faktisch durch die zunehmende Bildung keineswegs gestört oder abgelenkt worden ist.]

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. Howard & Paret (1976)]
    (Source)

(Source (German)). Alternate translations:

The invention of gunpowder, the constant progress of improvements in the construction of firearms are sufficient proofs that the tendency to destroy the adversary which lies at the bottom of the conception of war, is in no way changed or modified through the progress of civilisation.
[tr. Graham (1873)]

The invention of gunpowder and the advances continually being made in the development of firearms, in themselves show clearly enough that the demand for the destruction of the enemy, inherent in the theoretical conception of war, has been in no way actually weakened or diverted by the advance of civilization
[tr. Jolles (1943)]