In the course of this study, efforts will be made to trace briefly the development of the concept of aggression chronologically and its legal concept throughout history. We will consider the positions of states in different conditions, the effect of incidents on their positions and accounting for the growth factors involved, and also the efforts made to define the aggressor in international society. An analysis will be given of the legal effect and the significance of the achievements in international law. The principles which have been created for relations between states, as rule of law will become clear in the following chapters and the most important principle, the legal restraints on the use of force in inter state relations which demonstrates in the dangerous form of aggression will be handled