Wired reports that the Soviet Union actually had a doomsday device and kept it a secret.

“The whole point of the doomsday machine is lost if you keep it a secret!” cries Dr. Strangelove. “Why didn’t you tell the world?” After all, such a device works as a deterrent only if the enemy is aware of its existence. In the movie, the Soviet ambassador can only lamely respond, “It was to be announced at the party congress on Monday.”

So why was the US not informed about Perimeter? Kremlinologists have long noted the Soviet military’s extreme penchant for secrecy, but surely that couldn’t fully explain what appears to be a self-defeating strategic error of extraordinary magnitude.

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. Those who attack us will be punished.”

The logic is a tad fishy.  But it is not obvious that you should reveal a doomsday device if you have one.  It is impossible to prove that you have one so if it really had a deterrent effect you would announce you have one even if you don’t.  So it can’t have a deterrent effect.  And therefore you will always turn it off.

What you should worry about is announcing you have a doomsday device to an enemy who previously was not aware that there was such a thing.  It still won’t have any deterrent effect but it will surely escalate the conflict.  (via free exchange via Mallesh Pai.)