Garry Kasparov has been the most successful chess player in the world for 20 years. But at age 41, he is suddenly retiring from professional competition.
"Chess is a form of psychological warfare because at the end of the day you are fighting your opponent, you have to win," he said. "And by exposing yourself -- your energy, your fighting spirit at the board -- you are going through this form of mental torture."
Kasparov was born in Baku, the capital of Azerbaijan in the former Soviet Union. As a child he learned the basics of chess from his parents. As a product of the Soviet education system, he was soon sent to a government-sponsored chess school.
"I was attracted to the game of chess the first moment I saw the board and the pieces, and I just recognized that there was a great mystery at this 64 squares that was hidden in the 32 pieces, and I wanted to learn," he said. "I always wanted to learn more and more. For me it was a never-ending story."
By the time he was 22, Kasparov was the youngest world champion ever. Enthusiasts and experts alike said he was unstoppable. He has learned to deal with the anxiety.
"I don't think there was any tournament or single game that I wasn't nervous before," said Kasparov. "I think that being nervous is a part of motivating yourself or switching on your system. Because if you are not nervous then something is wrong inside of you. Means that your system is not ready for the big fight."
The millions of chess fans in the world remember that it was Kasparov who agreed to take on Deep Blue -- IBM's chess-playing computer. He won the first round but lost the rematch, and it still festers.
"The match has zero scientific value," Kasparov said. "Deep Blue was a fake from the scientific point of view because we never had an opportunity to investigate [its] decision making process."
It was only one incident in a stunning career. Kasparov is an inspiration to the 30 million to 40 million chess players in the world. He once challenged the world to a game on the Internet, and he has been a huge supporter of chess in the classroom.
"I think the game of chess is one of the most effective educational tools," he said, "It's not expensive at all, and it could teach kids so many unique qualities like logic, calculation, discipline, confidence."
Chess has always had its eccentrics. Kasparov, as a person, is simply fascinating. He is known for putting on his watch shortly before he goes in for the win.
"I used to wear a very heavy watch, it's my habit," he said. "I always used to take it off at the beginning of the match. And at the end, or when I saw the end was very near, I put back on my wrist."
Kasparov is leaving competitive chess for the very competitive world of Russian politics. He says that Russian democracy needs defending and it's being damaged by current President Vladimir Putin.
"I'm sad at the end of the day, but for me it's not a retirement," he said. "At 41, I'm not part of the Social Security debate yet. And I would rather see it as a transition. I did a lot -- probably more than anyone else at the chess board -- and I feel that all this experience, all the knowledge that had been accumulated over 30 years should be used more effectively somewhere else. I think my presence in Russian political life could make a difference for millions of people."
ABC News' Peter Jennings filed this report for "World News Tonight."