WE HAD A SCHEDULING ISSUE WITH THIS WEEK'S GUEST AND HE DID NOT APPEAR. WE WILL TRY TO RESCHEDULE. This week on History Happy Hour: President Truman’s choice to drop the atomic bomb is the most debated decision in the 20th Century. But what if he, himself, did not fully understand the decisions being made until after the atomic bomb was used.

Chris and Rick will talk to historian Alex Wellerstein about his highly regarded new book The Most Awful Responsibility: Truman and the Secret Struggle for Control of the Atomic Age.

Alex Wellerstein is an Associate Professor of Science and Technology at the Stevens Institute of Technology. He is also a visiting researcher at the Nuclear Knowledges program, Center for International Studies, Sciences Po, Paris. He is the author of Restricted Data: The History of Nuclear Secrecy in the United States, and he has written for The New Yorker, Atlantic, Harper’s Magazine, and many other venues. He is perhaps best known as the creator of the NUKEMAP, the world’s most popular online nuclear weapons effects simulator. He is also the author of the Doomsday Machines blog, and he has taught at Harvard, MIT, and Georgetown University.

This week on History Happy Hour: The little-known story of FBI agents who went undercover to hunt down U.S. traitors on foreign soil during World War II. The goal: to identify and capture U.S. citizens plotting against their own country in the shadows of war-torn Europe. To accomplish this, a small group of federal agents assumed new identities to infiltrate underground networks, interrogate key suspects, and conduct a secret manhunt as harrowing as any Hollywood cliff-hanger.

We’ll talk to Stephen Harding, author of G.I. G-Men: The Untold Story of the FBI's Search for American Traitors, Collaborators, and Spies in World War II Europe. HHH Alum Andrew Roberts says “Stephen Harding, America’s leading commentator on the extraordinary scenes that define the finale of World War II, has done it again."

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Stephen Harding is the author of ten previous books, including the New York Times bestseller The Last Battle and Last to Die. He is a longtime journalist specializing in military affairs. For nearly two decades he was on the staff of Soldiers, the official magazine of the US Army, reporting from Northern Ireland, Israel, Egypt, New Zealand, Bosnia, Kuwait, and Iraq. Currently he is editor-in-chief of Military History magazine.

This week on History Happy Hour: We travel back to the six critical months before Adolf Hitler seized power, when the Nazi leader teetered between triumph and ruin. As financial backers withdrew, the Nazi Party threatened to fracture. Hitler talked of suicide. The New York Times declared he was finished. Yet somehow, in a few brief weeks, he was chancellor of Germany.

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Timothy Ryback has written on history and politics for more than three decades. He is the author of Hitler’s Private Library, a Washington Post Best Book of the Year, and The Last Survivor, a New York Times Notable Book. His work has appeared in The New Yorker, The New York Times Magazine, The Wall Street Journal, The Atlantic, and the Financial Times. He is cofounder and director of the Institute for Historical Justice and Reconciliation in The Hague.