Since the end of the Cold War, it's been easy to see nuclear competition as a thing of the past. As the dust settles over Iran—as Russia rattles the nuclear saber in Ukraine—it's increasingly clear that the question of nuclear weapons has been re-opened. Join Samantha and guest Matthew Downhour as they talk the fundamentals of nuclear strategy, how "red lines" are not natural but socially constructed—and how Trump's reckless actions have degraded the social order that has kept the world from nuclear war since 1949.