“The Twenty Years’ Crisis, 1919-1939: An Introduction to the Study of International Relations” by Edward Hallett Carr is a foundational text in international relations theory. Published in 1939, it critiques the idealist approach to international politics, which dominated thinking after World War I. Carr argues that the post-World War I idealism, embodied in efforts like the League of Nations, was unrealistic because it ignored power politics and the importance of national interests. He introduces a realist perspective, emphasizing that international relations are driven by power and self-interest rather than moral ideals or legal norms. Carr’s work laid the groundwork for modern realism, contrasting it with utopianism, and offered a critique of the liberal international order that failed to prevent the rise of totalitarian regimes and the outbreak of World War II.