The rules for modern life in the international community were written in religious and secular circles. They were developed over a long period of time and enriched by the contributions of great thinkers: from St. Augustine to John Paul II, from the Dominican de Vitoria to Grotius and de Vattel. They all had a common goal. The history of nations and states has been marked by wars and peace, and has also included just wars, which in the current era are considered outdated. History has justified the use of arms, which has entered modern international law but is subject to certain conditions. International law is the means worthy of man and peoples to avoid the arbitrary use of force and to resolve disputes, but it must be able to rely on an authority with effective powers. Many questions remain, but it is certain that we are obliged to consider the subject of war with a completely new mindset.