Mandelbaum argues that the 25 years after the end of the Cold War were uniquely peaceful thanks to three forces: U.S. liberal hegemony, the spread of democracy, and rising economic interdependence. This was not merely a “realist peace,” that is, a momentary pause in geopolitics or a reflection of U.S. unipolarity. Around the world, there were glimmers of a “Kantian peace,” rooted in shared interests and values among liberal democratic states. Why did it unravel? Mandelbaum points the finger at Russia’s aggression in Europe, China’s expansionism in Asia, and Iran’s tendency to sow chaos in the Middle East. Interestingly, Mandelbaum spares the United States most of the blame. He argues that although NATO expansion did, as many suggest, antagonize Russia, today’s great-power revisionism was caused primarily by the spread of democracy. Ironically, he argues, if democracy had not shown such worldwide appeal, illiberal states would have pursued less aggressive policies in response. World peace, it seems, will have to wait until democracy wins a more complete victory.