Daniel Ellsberg in his youth and Daniel Ellsberg in his age are the same man—a born worrier quick to spot trouble, take alarm, and issue warning. He is best known for worrying about the American war in Vietnam, which time in the war zone convinced him was a crime, and for doing what he could to bring it to an end. In that case he copied and illegally released a huge collection of secret documents about the war, which came to be known as the Pentagon Papers. But Vietnam was not the first or the biggest thing that worried Ellsberg after he went to work in his late twenties as an analyst for the RAND Corporation in 1959. His first and biggest worry was the American effort to defend itself with nuclear weapons.