It's supposed to be the stuff of science fiction: A device that triggers a nuclear holocaust in the event of a U.S. strike against Russia.
But the "Dr. Strangelove"-esque technology isn't just fantasy. The Cold War-era Soviet "doomsday machine" was -- and might still be -- very much a reality.
From interviews with former Soviet arms officials and Defense Department documents, Nicholas Thompson, a senior editor for Wired magazine and author of "The Hawk and The Dove: Paul Nitze, George Kennan, and the History of the Cold War," learned that the system was built 25 years ago to ensure a nuclear retaliation if Russia were attacked by the U.S.
When triggered by an elaborate system of sensors placed around Russia, the program was designed to launch a fleet of missiles at major targets across the U.S. Some experts estimate that a Russian counter-strike could have killed more than one hundred million Americans.
And though the Iron Curtain was lifted more than a decade ago, it's believed that the "doomsday" system was never retired, according to Thompson.
"The Soviets really did fear that the U.S. was going to launch a nuclear strike," he said. "It's still in place, but it's not as though they're sitting around waiting for America to strike. It's on lower alert."
The top-secret Russian program, he continued, virtually guaranteed the ability to strike back, even if the entire chain of command had been wiped out.
Now that the Cold War is over, the closely-guarded system, code-named Perimeter, is no longer a secret. Experts on the Russian military have published articles about it since the early 1990s.
But top American and Russian officials are still reluctant to discuss it, Thompson said.
In a piece written last month for Wired, Thompson said that when he told former CIA director James Woolsey about the USSR's doomsday device, he responded, "I hope to God the Soviets were more sensible than that."
For his article and book, Thompson spoke at length with Valery Yarynich, a former colonel with the Soviet Strategic Rocket Forces and Soviet General Staff, who helped build the Perimeter system.
But Thompson said that the program is still so under wraps that Yarynich is concerned that his transparency puts him at risk. Apparently, Thompson wrote, a Russian official who spoke with Americans about the program died after a mysterious fall down a flight of stairs -- an ominous sign for others considering speaking.
The Perimeter system Yarynich helped build involved four steps. Designed for crisis situations, officials first had to turn the program on. Once activated, it would continuously scan for signs of a nuclear explosion with seismic, radiation and air pressure sensors.
If the sensors detected a nuclear attack, the program would attempt to contact political and military leaders. If the system could not communicate with the leaders, then it would determine that it was time for retaliation.
But the "doomsday machine" wasn't totally automatic and computerized.
Once the first three conditions were met, authority to launch the counter-attack returned to humans -- officers stationed beneath the surface of the Earth in a concrete bunker, presumably protected from any nuclear blast.
The last safeguard against a possible apocalypse, those officers were trained to unleash command missiles that would fly across the country and wirelessly deliver launch orders to any Russian missiles that had survived a first strike.
Even if the Kremlin had crumbled and all communications had been knocked out, those remaining weapons would begin the assault on the U.S.
David E. Hoffman, author of the recently-released "The Dead Hand: The Untold Story of the Cold War Arms Race and Its Dangerous Legacy," said those bunker-protected officers have been the subject of much debate.
Some argue that the good soldiers, drilled to follow orders, would function just like cogs in a machine and release the command missiles without hesitation, he said. Others maintain that they would deliberate before ordering the onset of a nuclear Armageddon.
"[They were] the so-called human firewall," he said. "They had criteria… It wasn't fully automatic."
The point of the system was not to deter the U.S. from striking, he said, but to relieve the pressure on aging leaders. He said its goal was to give leaders extra time to figure out how to respond in a crisis.
"The idea here was if I turn on the switch, I give the decision to somebody else," Hoffman said. "If I'm wiped out, I know there will be retaliation. If it's a flock of geese, I won't make a mistake."
"There was always this quest for a speedier response in an emergency," he said. "If you could get the command there faster, you could give the commander more time to think."
The Russians did consider a more frightening option: A totally automatic, computer-driven nuclear retaliation system.
Called Dead Hand, the program transferred all power to launch a counter-attack from man to machine. But the Russians ultimately rejected that system, according to Hoffman.
The most alarming piece of the equation, he said, is that the U.S. didn't know anything about it.
Notoriously secretive to begin with, the Russians were concerned that if the U.S. knew about Perimeter, they would attempt to disable it, Hoffman and others said.
"The scary part to me is that they built it and nobody knew," he said.
Although he acknowledged that given the top-secret status still attached to this program in Russia, details are hard to come by, Hoffman said that there have been some signs the Russians have started to shut down parts of the system.
But other Russian military experts say that not only is the system most likely still in place, it has received upgrades over the years.
"As far as I know, the system remains in essentially the same status as it was," said Bruce Blair, president of the Washington, D.C.-based think tank World Security Institute and one of the first to write about the Perimeter system in the early 1990s.
"The U.S. and Russia keep thousands of weapons on launch-ready alert," he said. "I think there's no reason to believe that this system would have been shut down."
Like Hoffman, he said Perimeter was intended to take pressure off of Russian leaders.
"It was a system that provided some confidence that the Soviet nuclear forces could be launched even if they didn't make a fast decision," he said. "By relieving pressure it meant that the Russians were less likely to launch a nuclear attack on false warning."
In a sense, he said, "That made everyone safer."
But, he emphasized that Perimeter's continued existence is "a symptom of a continuing grave danger."
"The fact that the Russians have Perimeter still in operation reflects that the two sides have launch on warning as their operating postures and quick launch continues to be their M.O.," he said. "We need to stand down our Cold War postures, which keep us at risk of destruction caused by false alarm or caused by unauthorized action or even by cyber-terrorism."