Historian Graff, whose book Watergate was a finalist for the Pulitzer Prize, spent an intense year writing The Devil Reached Toward the Sky (Avid Reader, Aug.), about the Manhattan Project and the dropping of the atomic bomb. The bestselling author of 10 books, who also hosts the Long Shadow podcast and writes the popular newsletter Doomsday Scenario, discusses the bomb’s legacy and explains why he likes messy history.

This is your third book-length volume of oral history, after The Only Plane in the Sky (about 9/11) and When the Sea Came Alive (about D-Day). Why did you want to write it?

This year marks the 80th anniversary of the end of WWII. At this moment we effectively have every first-person memory that we’ll have of the war, and my goal was to tell those stories in the voices of the people who lived them. With my book, I tried to capture what it was like to learn the secrets of the atom and embark on the Manhattan Project at a moment when we didn’t know what would happen in the war. We didn’t know if Hitler would build a bomb first, or if the bomb would work at all.

The book is based on archival research and masterfully draws from a range of sources including memoirs, government reports, personal letters, testimonials, and more. How did you pull the material together?

Doing oral history is the opposite of doing normal book writing because it’s subtractive rather than additive. I’m from Vermont and I talk about it as similar to making maple syrup. You start with this enormous vat of sap then spend months boiling it down to the essence of the story. I started this book after months of research with a manuscript that was about 1.4 million words. Then I sat there and boiled off between 90 and 95 percent of that manuscript to get it down to the essence. It brings together about 500 voices spanning scientists, soldiers, government officials, and many others, as well as hundreds of voices of the Japanese survivors of Hiroshima and Nagasaki, and those who fought on the Japanese side as well.

The Manhattan Project wasn’t contained to Los Alamos in New Mexico. There were other facilities, including secret cities in Washington State and Tennessee that employed tens of thousands of workers, from scientists to cooks and janitors. How did you work to capture the voices of everyday folks when composing this book?

We often oversimplify the story of the Manhattan Project to J. Robert Oppenheimer and his band of merry physicists on a mesa at Los Alamos. But the majesty of the Manhattan Project is in the industrial might that the U.S. brings to bear on the creation of the atomic bomb. Workers tolled in secret facilities sometimes for years without ever knowing the thing they’re doing to contribute to the war effort, and that to me is what’s incredible about the scale of the Manhattan Project. When I’m sorting through testimonials and memories, what I’m searching for is the extraordinary and the ordinary. I’m looking for people who have the most incredible experiences, but I’m also looking for the most ordinary accounts. Those are the voices that are easiest to write out of history.

One of the stories I really love is what came to be known as the Calutron Girls. During WWII there was a massive labor shortage and they ended up recruiting recent high school graduate women out of the mountains of Tennessee to run the uranium refining process, using machines called calutrons. They went on to be the majority of the workforce in this specialized process.

What do you like about writing oral history?

It captures the messiness of history. I come to history as a journalist and one of the things that being a journalist teaches you is that events are messy and unclear to people as they live through them. Oral history lets you understand history in a different way.

What’s the legacy of the Manhattan Project, and what’s its relevance to the modern moment?

The bombings of Hiroshima and Nagasaki are events so terrible that the central organizing principle of geopolitics ever since has been to avoid ever using those weapons again. And yet here, in the middle of the 2020s, we’re probably at a moment where we’re closer to nuclear danger than most people realize. The Manhattan Project is also important in how it rewrites the relationship between government and science. Before WWII we had no sense of industry and science and technology as a core national strength. What we’re witnessing now, as the Trump administration tries to gut higher education by cutting science and medical research funding and reversing the tradition of international students and immigrants coming to the U.S. to study, is a suffocation of the country’s greatest strength.

This book stands as a powerful duology with your previous book, When the Sea Came Alive, about D-Day. Taken together, what do you think they say about WWII and American history?

What stands out if you read them back to back is the way that these two events, D-Day in Europe, and the Manhattan Project and the dropping of the atomic bomb in the Pacific, tell the story of the invention of the American century: the idea of America in its post-war mythology as the leader of the free world. You see the roots of the rest of the 20th century in these two events, and the mythology that grows up around them, about America as the unparalleled economic hegemon and inventor of what comes next in the world.

You’re an avid collector of historical memorabilia. What kinds of objects do you collect?

I have this amazing 1890s carriage barn that serves as my office and have filled its walls with posters and broadsides and newspapers from historical events, and the bookshelves themselves are filled with trinkets and artifacts. I have coffee mugs from secret government bunkers, Richard Nixon campaign posters, a mini grandfather clock honoring George Dewey, hero of the Spanish-American War. I love antique stores and used bookstores, and I’ve always been an eBay troller.

You’ve written 10 books and co-authored others. What do you do for fun, or are you always writing?

When I’m in between work reading, I use that time to read more widely in nonfiction. The least surprising thing is that I have in fact always been that person. When I was in elementary school my teacher told me she’d never met any student who enjoyed nonfiction as much as I did. That’s still true of me almost 40 years later. And I have far more books that I’d like to write that I’ll ever get around to writing.

Elaine Szewczyk’s writing has appeared in McSweeney’s and other publications. She’s the author of the novel I’m with Stupid.