What Motivates States in Their Behaviour

There is a fundamental difference between domestic politics where there are high authorities, the police, courts, governments and international relations. As countries such as Ukraine and others have experienced recently, you do need to be prepared for potentially the worst case scenario that your neighbours turn hostile. International law has accumulated over the years that constrains the behaviour of states. But you can never be sure as a world leader that international law alone will guarantee your survival. So you need to have a backup.