International relations characterise domestic decisions more and more, and political implementation is increasingly determined by geopolitical considerations. The survival of states in this complex environment depends on a proactive assessment of the international situation. Geopolitics is thus becoming the determining factor in international relations, with five-dimensional thinking becoming a political imperative. The first part of the textbook provides an overview of the fundamentals of international relations. The second part deals with global fields of geopolitics, including outer space and cyberspace. Klemens H. Fischer is Professor of International Relations and Geopolitics at the University of Cologne. He is Vice President of the Austria Institute for European and Security Policy, Vienna, and member of the International Institute for Strategic Studies, London. He can draw on thirty years of experience in the field of international relations.