34 years ago, on 26 September 1983, the world was saved from potential nuclear disaster, but few people today know about the man who saved it.
In the early hours of the morning, the Soviet Union's early-warning systems detected an incoming missile strike from the United States. Computer readouts suggested several missiles had been launched.
The Soviet government’s policy in the event of a US nuclear attack was to launch an immediate and all-out retaliatory strike in accordance with the principle of Mutually Assured Destruction.
But duty officer Stanislav Petrov - whose job it was to register apparent enemy missile launches - decided not to report them to his superiors, and instead dismissed them as a false alarm.
This was a breach of his instructions, a dereliction of duty. The safe thing to do would have been to pass the responsibility on, to refer up, but his decision may have saved the world.
"I had all the data [to suggest there was an ongoing missile attack]. If I had sent my report up the chain of command, nobody would have said a word against it." he said in an interview to the BBC 30 years after that overnight shift.
"There was no rule about how long we were allowed to think before we reported a strike. But we knew that every second of procrastination took away valuable time; that the Soviet Union's military and political leadership needed to be informed without delay. All I had to do was to reach for the phone; to raise the direct line to our top commanders - but I couldn't move. I felt like I was sitting on a hot frying pan".
Although the nature of the alert seemed to be abundantly clear, Mr Petrov had some doubts. A group of satellite radar operators told him they had registered no missiles, but those people were only a support service.
The protocol said, very clearly, that the decision had to be based on computer readouts, and that decision rested with him, the duty officer. But what made him suspicious was just how strong and clear that alert was.
He had just minutes to decide whether to assess the attack as genuine and inform the Kremlin that the United States was starting World War Three - or tell his commanders that the Soviet Union's early warning system was faulty. Guessing that a genuine American attack would have involved hundreds of missiles, he put the alarm down to a computer malfunction.
Mr Petrov called the duty officer in the Soviet army's headquarters and reported a system malfunction.
Lt Col Petrov was vindicated when an internal investigation following the incident concluded that Soviet satellites had mistaken sunlight reflected on clouds for rocket engines.
He kept silent about the incident for 10 years. "I thought it was shameful for the Soviet army that our system failed in this way." he says. But, after the collapse of the Soviet Union, the story did get into the press.
Mr Petrov received several international awards. But he did not think of himself as a hero.
"That was my job", he said. "But they were lucky it was me on shift that night."
Indeed the whole wrold was "lucky" that duty officer Stanislav Petrov was on the job on that fateful day in 1983, otherwise, nuclear war might have broke out between the US and the USSR and the whole world would have turned into nuclear wasteland.