Classical realism is based on the empirical analysis of human nature and international politics. It is influenced by thinkers like Sun Tzu, Thucydides, Machiavelli, and Hobbes. Classical realists believe that sovereign states operating in an anarchic international system are the key actors, and they are primarily concerned with their own security and survival. In this self-help system without any overarching authority, conflict among states driven by their struggles for power is an inevitable reality.