A timely and fascinating look at the creation and history of the 1928 Paris Peace Pact—an often overlooked but vital treaty that was created to outlaw wars of aggression and provide the unprecedented stability we live under today.

Everyone knows that our world does not lack for bloody conflict. Yet it’s important to remember that while war was deemed the legitimate means of settling disputes among nations for much of human history, today a robust ecosystem of international institutions and interlocking treaties has helped make inter-state war the exception, rather than the rule. Remarkably, this very development can be traced to the afternoon of August 27, 1928.

The Worst Crime of All is an exceptionally and thoroughly well-researched account of the people, ideas, and harrowing events that led to the Kellogg-Briand Act (aka “The Paris Peace Pact”). Oona Hathaway and Scott Shapiro tell the amazing history of the Pact through a remarkable, little known cast of global thinkers—Hugo Grotius, Salmon Levinson, Nishi Amane, Samantha Power, among others—who sat down to create one of the most transformative treaties in history. They detail the brutal world of conflict the Peace Pact helped extinguish, and the subsequent era where carrot and stick were far more likely to take the form of tariffs and sanctions than tanks and gunships.

At a time when confidence in institutions like the UN and WTO is on the wane, The Worst Crime of All examines with renewed appreciation an international system that has outlawed wars of aggression and brought unprecedented stability to the global map. Accessible and gripping, this book will change the way we view the history of the twentieth century—and the way we read the news each morning.