Theory might appear boring, but theoretical insights help us to understand international relations and interpret events. By applying a theory that is based on many years of research into actual cases, we can explain why certain geopolitical changes bring more stability to the world or, on the contrary, greater instability. Theory helps us to understand the Ukraine crisis of 2014 and the politics of China in the South and East China Seas.

The most important school of thought in international relations is the Realist school. According to this school, international relations are determined by power and power politics. Put simply, this school assumes that the lack of a supranational authority above states creates a situation in which ‘might is right’. There is a continuous struggle between the most important actors – states – all of which have a tendency to advance their own interests and focus primarily upon their own survival. As suggested earlier, in this power game the superpowers and the great powers make the rules. Hans Morgenthau (1904-1980) was one of the founders of the Realist school. For decades, his book Politics Among Nations: The Struggle for Power and Peace (1948) has been a standard work for university students of international relations. Morgenthau emphasized the national interest and attributed the nature of international relations to human behaviour.

One key theme is the security dilemma. The behaviour of states produces a security dilemma in which one state's or a coalition of states’ striving for more security provokes a similar reaction on the part of another state or coalition of states, if the latter feel threatened by this. Thus by definition, an increase in one country's security comes at the cost of another country's security, which subsequently takes measures to increase its own security. The term ‘security dilemma’ was first used by the German thinker John H. Herz in his book Political Realism and Political Idealism (1951). If we view the expansion of NATO and the European Union after the Cold War through the lens of Realism and the security dilemma, we can explain why Russia annexed the Crimea in 2014: Russia felt threatened by the advance of the West.