In 1971 when Daniel Ellsberg leaked the Pentagon Papers and revealed the true story of American involvement in Vietnam, he was holding on to a much larger and more terrifying set of American secrets than he was letting on.

Ellsberg had to wait almost fifty years to bring them to light. What those secrets were and why they remained hidden for so long are revealed in his new book The Doomsday Machine: Confessions of a Nuclear War Planner.