Before launching any retaliatory strike, the system had to check off four if/then propositions: If it was turned on, then it would try to determine that a nuclear weapon had hit Soviet soil. If it seemed that one had, the system would check to see if any communication links to the war room of the Soviet General Staff remained. If they did, and if some amount of time - likely ranging from 15 minutes to an hour - passed without further indications of attack, the machine would assume officials were still living who could order the counterattack and shut down. But if the line to the General Staff went dead, then Perimeter would infer that apocalypse had arrived. It would immediately transfer launch authority to whoever was manning the system at that moment deep inside a protected bunker - bypassing layers and layers of normal command authority. At that point, the ability to destroy the world would fall to whoever was on duty.
Isn’t the whole point of having a doomsday machine that you let your enemies know about it? It seems the Soviets didn’t.
The silence can be attributed partly to fears that the US would figure out how to disable the system. But the principal reason is more complicated and surprising. According to both Yarynich and Zheleznyakov, Perimeter was never meant as a traditional doomsday machine. The Soviets had taken game theory one step further than Kubrick, Szilard, and everyone else: They built a system to deter themselves. By guaranteeing that Moscow could hit back, Perimeter was actually designed to keep an overeager Soviet military or civilian leader from launching prematurely during a crisis. The point, Zheleznyakov says, was “to cool down all these hotheads and extremists. No matter what was going to happen, there still would be revenge.” […]
Given the paranoia of the era, it is not unimaginable that a malfunctioning radar, a flock of geese that looked like an incoming warhead, or a misinterpreted American war exercise could have triggered a catastrophe… Perimeter solved that problem. If Soviet radar picked up an ominous but ambiguous signal, the leaders could turn on Perimeter and wait. If it turned out to be geese, they could relax and Perimeter would stand down. Confirming actual detonations on Soviet soil is far easier than confirming distant launches. “That is why we have the system,” Yarynich says. “To avoid a tragic mistake.”