The study of international relations, as theory, can be traced to E. H. Carr's The Twenty Years' Crisis, which was published in 1939, and to Hans Morgenthau's Politics Among Nations published in 1948.
Studi hubungan internasional sebagai teori sudah ada sejak buku The Twenty Years' Crisis karya E. H. Carr diterbitkan pada tahun 1939 dan buku Politics Among Nations karya Hans Morgenthau terbit tahun 1948.