"There were 28 or 29 levels of security. After the target was identified, he had to go through all these 'checkpoints'. I wasn't sure if that was possible under the circumstances," says the retired officer.
Petrov called the duty officer at Soviet Army headquarters and reported a system failure.
If he was wrong, the first nuclear explosions would have occurred minutes later.
"Twenty-three minutes later I realized that nothing had happened. If there had been a real attack, then I would have known about it. It was a huge relief," he says with a smile.
"Lucky it was me"
Soviet protocol stated that the military should respond to one nuclear attack with another.
Now, 30 years later, Petrov believes the chances were 50-50. He admits he was never entirely sure the alert was false.
He says he was the only officer on his team who had received a civilian education. "My companions were professional soldiers, they were taught to give and obey orders," he said.
