The aims and goals of war have drastically changed during the recent decades. The prohibition of the use of force fixed in the Charter of the United Nations became a real challenge to many states. Nevertheless, we observe regular use of force in international relations. Though "classic" interstate wars became rather rare, the states continue to solve their political problems by exploiting the armed forces. In these circumstances it is problematic to explain the use of force from the legal point. That is why we talk so much about "preventive self-defence", "humanitarian intervention", "the responsibility to protect" and some other controversial concepts. One of the most disputable among them is a "just war" concept, which has practically not been analyzed in our domestic doctrine. However, the western school of international law is actively implementing precisely the legal dimension of the "just war" concept. Of course, the concept itself is extremely political, but the consequences of its practical implementation may have a great impact on contemporary international law, as it tries to legitimize the use of force in circumvention of the Charter of the United Nations. Because of the huge importance of the question, the analysis of the concept seems extremely actual.