The historical roots of the most important problem of our time are revealed - war or peaceful relations between different states and peoples. An attempt was made to consider this problem on the material of world history. The analysis is carried out on examples of the collision of Ancient Rome and early Christianity, Byzantium and the Arab caliphate, medieval papacy and empire; on the examples of wars, the participants of which were Turkish Janissaries and German Landsknechts, British pirates and Spanish inquisitors, and in modern times - the forces of reaction and national and social liberation.