I didn’t know about this. Did you?

The Soviets were especially worried about the decision that an ailing leader like Leonid Brezhnev would have to make if faced with a warning of nuclear attack. He would have only minutes to decide, and the alert information might not be clear or certain. What if he hesitated? What if he made a mistake and issued a launch order based on a faulty warning?

The Soviet designers responded with an ingenious and incredible answer. They actually built a doomsday machine that would guarantee retaliation — launching all the nuclear missiles — if the leader's hand went limp. Now some details of the system have come to light in documents and interviews with officials who were involved. I have detailed the history and rationale of this doomsday machine in my new book. The system was in effect a switch that would allow the Soviet leader to delegate the decision about retaliation to someone else. An ailing general secretary could activate the system if he received a warning of attack, and thus might avoid the mistake of launching all the nuclear missiles based on a false alarm. Should the enemy missiles actually arrive and destroy the Kremlin, there would be guaranteed retaliation.

Originally, the Soviet Union devised a totally automated, computer-driven retaliatory system known as the Dead Hand. If all the leaders and all the regular command systems were destroyed, computers would memorize the early-warning and nuclear attack data, wait out the onslaught, and then order retaliation without human control. This system would, basically, turn over the fate of mankind to machines.

However, this idea was too frightening for the Soviet designers and leaders, and they did not build it. Instead, they constructed a modified system, quite elaborate, known as Perimeter. Instead of machines, Perimeter had a human firewall to make the fateful decision — a small group of duty officers buried deep underground in a concrete globe-shaped bunker. If certain conditions were met, including seismic data showing that a nuclear explosion had already detonated on Soviet soil, and if the Kremlin communications were down, these duty officers could launch a series of small command rockets in superhardened silos. Like robots, the command rockets would then fly across the country and issue the launch order to the intercontinental ballistic missiles. The Perimeter system was tested in November 1984 and put on combat duty in early 1985. But the Soviet Union kept this system a secret, and many features of it were not known to the United States until after the Cold War…

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