Buzan’s security studies use a “multilateral” perspective to bring together neo-realism, materialism and the “English School”, as well as the Copenhagen School and sociological approaches like social constructivism. He also adds historicist and international political economy methods to this mix. His notable contributions include his “new comprehensive security analysis framework” and “regional security composite theory”. The former emphasizes multilevel, multi-domain and multi-agent analysis that looks at the interaction between polarity and identity, while the later emphasizes security interdependency, friend/enemy models and powers structures that create the “security complex” that is the core of international security. Buzan’s theories and ideas have had a profound impact on the integration of modern security studies, particularly security theory.