The end of the Cold War demonstrated the historical possibility of peaceful change and seemingly showed the superiority of non-realist approaches in International Relations. Yet in the post-Cold War period many European countries have experienced a resurgence of a distinctively realist tradition: geopolitics. Geopolitics is an approach which emphasizes the relationship between politics and power on the one hand; and territory, location and environment on the other. This comparative study shows how the revival of geopolitics came not despite, but because of, the end of the Cold War. Disoriented in their self-understandings and conception of external roles by the events of 1989, many European foreign policy actors used the determinism of geopolitical thought to find their place in world politics quickly. The book develops a constructivist methodology to study causal mechanisms and its comparative approach allows for a broad assessment of some of the fundamental dynamics of European security.