Study of the relations of states with each other and with international organizations and certain subnational entities (e.g., bureaucracies and political parties).
It is related to a number of other academic disciplines, including political science, geography, history, economics, law, sociology, psychology, and philosophy. The field emerged at the beginning of the 20th century largely in the West and particularly in the U.S. as that country grew in power and influence. The study of international relations has always been heavily influenced by normative considerations, such as the goal of reducing armed conflict and increasing international cooperation. At the beginning of the 21st century, research focused on issues such as terrorism , religious and ethnic conflict, the emergence of substate and nonstate entities, the spread of weapons of mass destruction and efforts to counter nuclear proliferation, and the development of international institutions.