Chad L Williams has written a brilliant biography of WEB Du Bois, a civil rights powerhouse widely regarded as America’s most important Black intellectual. Williams speaks and writes with a warmth and authority which have made him a star at Brandeis University, where he is the Samuel J and Augusta Spector professor of history and African and African American studies.

The Guardian caught up with him just after he arrived in his hometown, San Francisco, where he was combining promotion for The Wounded World with a reunion with his sister and his parents, both retired attorneys.

Williams lives in Needham, Massachusetts, with his wife, Madeleine Lopez, who directs the Center for Inclusive Excellence at Regis College, and their three children.

“I thought I was going to go to law school but then I realized I didn’t want to be like my parents,” Williams said. “My first encounter with Du Bois was during my freshman year at UCLA, in a course on African American nationalism when I read [Du Bois’s 1903 classic] The Souls of Black Folks.

“I was blown away. I remember not knowing what to make of this very strange book that had all of these powerful metaphors in it. It was really undefinable as far as discipline. It had history, sociology, philosophy, music. It is truly one of those timeless, classic books.

“I started reading his other books like Black Reconstruction in America and really came to appreciate him as the most significant Black intellectual and scholar activist in American history.”

To Williams, Du Bois was “singular” because of the sheer span of his life: “Ninety-five years; born in 1868 during the presidency of [Andrew] Johnson, during Reconstruction, he dies the day before the March on Washington, in Ghana in 1963. He really encapsulated the struggle for Black freedom and equality throughout the 20th century in the United States and throughout the broader African diaspora. I never thought I’d write a whole book about Du Bois. But yeah, it did happen.”

Williams was a graduate student at Princeton when he first went to University of Massachusetts-Amherst, where most of Du Bois’s papers are in a library named in his honor. He saw a reference to “Du Bois world war I materials” and asked to see them.

“I figured maybe I’ll get a couple of folders and [the librarian] returned with six microfilm reels. And I think, ‘What could this possibly be?’ I load this first reel and I see this manuscript which I knew nothing about. It was over 800 pages long. In addition to the manuscript, all of his research materials and all of his correspondence related to this book entitled The Black Man and the Wounded World.

“He worked on it for two decades and no scholar had ever talked about it. I was stunned. This was this huge aspect of his life and career and scholarship which had been overlooked. From that moment I was hooked on understanding it. It would have been the definitive history of [Black soldiers] in world war I and one of Du Bois’s most significant works of scholarship – but he never completed it.”