This study, a realist interpretation of the long diplomatic record that produced the coming of World War II in 1939, is a critique of the Paris Peace Conference and reflects the judgment shared by many who left the Conference in 1919 in disgust amid predictions of future war. The critique is a rejection of the idea of collective security, which Woodrow Wilson and many others believed was a panacea, but which was also condemned as early as 1915. This book delivers a powerful lesson in treaty-making and rejects the supposition that treaties, once made, are unchangeable, whatever their faults.