On this episode: How does the United States use, or more precisely avoid using, its fearsome arsenal of nuclear weapons? How did we arrive at a world in which so many countries are armed to the teeth with nukes? What can we expect from North Korea as negotiations continue? We revisit the Cold War this week with Joe Cirincione, author of Bomb Scare: The History and Future of Nuclear Weapons, and president of Ploughshares Fund.