Chess legends Garry Kasparov and Anatoly Karpov reignite one of the greatest rivalries in the history of chess this week with a re-match of their classic 1984 world championship contest.

The two Russian grand masters, who are widely considered the greatest chess players ever, will play the first of a 12-game re-match in Valencia, Spain, starting on Tuesday, 25 years after the pair first competed for the world title.

The event will be broadcast live on Valencia's regional government website (www.gva.es) with organizers expecting up to 10 million chess fans to follow the matches.

The epic 1984 duel ended in controversy and without a clear winner when the World Chess Federation unexpectedly called off the match after five months of play, citing health concerns for the players who were both representing the Soviet Union.

Then reigning champion Karpov, now 58, had won five matches while Kasparov, now 46, had won three with 40 other games ending as draws. Both players said they wanted to play on.

Kasparov, who is now a politician and vocal opponent of Russian Prime Minister Vladimir Putin, claimed the match was called off to save Karpov from defeat -- and a nervous breakdown -- as the match had come to symbolize the competing forces then at play in the Soviet Union. Karpov was a darling of the Soviet establishment.

The World Chess Championships restarted in Moscow about a year later and Kasparov went on to snatch the world crown from Karpov, becoming the youngest world champion with his win seen as youth triumphing over the aging Soviet empire.

Kasparov held the title until 1993 when he broke away from the World Chess Federation (FIDE) to form the Professional Chess Association while Karpov was FIDE world champion from 1993 to 1999. The chess world title was only unified in 2006.

Kasparov, who retired from professional chess in 2005, said the match in Valencia would be more of a ceremonial tournament with a time-limit on moves.

In this case, nostalgia will be a positive thing, and the duel will serve to put a spotlight on chess again, just like 25 years ago. In any case, we're both capable of playing high-quality chess, he told El Pais newspaper.

He has been training in the Norwegian capital Oslo with 18-year-old chess prodigy Magnus Carlsen while Karpov has been training with a group of world-class players and with a computer, according to organizers.

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