Although the years 1917-1921 are often glossed over in textbooks on American history, it was the bloodiest period of political violence the United States since the Civil War. Thousands of Americans were imprisoned for things they had written or said. With the blessing of the Justice Department, vigilante groups roamed the streets of major cities, arresting leftists and alleged draft-dodgers. Army troops patrolled the streets with machine guns and, in one case, a tank. Government press-censorship banned more than 400 issues of American newspapers and magazines from the mail, and they shut down many others entirely. More Black Americans were murdered by white supremacists and mob violence in 1919 than in any year since the end of slavery. In this talk, Adam Hochschild discussed what ignited this almost unparalleled storm of repression and violence: the US entry into the World War I, in April 1917. That, he argues, took the lid off a number of conflicts that had long been simmering in American life — conflicts between business and labor, racial identities, and nativists and immigrants.