Since the 1990s,changes in international relations have brought about the transformation of the security concept and also
important discussions on whether to narrow or extend the security agenda.Mingled with the debate over the"third wave,"this discussion highlights the security studies of constructivism as represented by the European Copenhagen School and the American School led by Barry Posan and scholars like Peter Kazenstein respectively.Compared with the American school,the Copenhagen School,which boasts the Security Community Theory and the Non-
securization Theory,has become the most
important school in the field of security studies in the West.It holds that security is nothing but a particular type of politics applicable to a wide range of issues.With the approach of social constructivism,the Copenhagen School provides insight into an understanding of under what conditions security can be achieved.This approach has successfully accommodated the security research agenda of the traditionalists.Finally,the essay points out how the theory of regional complex security remains relevant in today's world.