President Harry Truman was perhaps the most influential American president with regards to the path of global nuclear history. Over the course of his presidential term (1945-1953), he oversaw the first (and so far only) use of the atomic bombs in war, the creation of the system of unilateral nuclear use authority, the creation of the hydrogen bomb, and the buildup of the US nuclear arsenal. But this new book argues that nearly every aspect of the current understanding of these events, and his broader nuclear legacy, has been dramatically misunderstood by both the general public as well as other scholars. Truman was, rather, perhaps the most anti-nuclear president of the 20th century, and did more to push and reinforce the idea that nuclear weapons could never be used again than perhaps any leader since, and during a key period in which it was by no means an obvious conclusion. Using new historical and archival research, this book attempts to make the case for this argument while resolving the apparent and obvious paradoxes that it presents, offering up a new understanding of how we ought to understand Truman's nuclear legacy, especially in our current geopolitical moment.