This article analyzes the evolution of the concept of war in the 20th century from different views. The analysis explores the aspects that have characterized war and the different perceptions it has aroused in the last century, as the changes in these perceptions have, in turn, generated an alteration in the instrumental use of the war conflict. Ultimately, the study seeks to analyze the extent to which war is an instrument of change in societies to the beginning of the 21st century, especially in the fields of psychological perception, state forms, the structure of societies, and international relationships.