On May 3, 1946, at the former Army Ministry in central Tokyo, 11 international judges gathered for an extraordinary legal proceeding. The building’s auditorium had been refashioned into a courtroom, klieg lights and cables for broadcasters installed. As the judges donned their robes, they learned that 26 inmates—former military and civilian leaders of wartime Japan—had arrived from Sugamo Prison. “The International Military Tribunal for the Far East is in session and is ready to hear any matter brought before it,” the court’s marshal announced, and with that the highly anticipated trial of alleged Japanese war criminals was under way.

Gary Bass’s “Judgment at Tokyo” is the story of the tribunal—the politically fraught path to its creation, the trial itself and its long-term impact. Mr. Bass, a prolific author and a professor of politics at Princeton, says that he wrote the book in part because, while the Nuremberg trials of Nazi Germany’s leaders have been richly documented—indeed, “Nuremberg” has become synonymous with war-crimes prosecution—far less is known about what happened in the Tokyo courtroom.