From Wikipedia article World Chess Championship
Chaos
Not long after Kasparov became champion, the Soviet Union collapsed, freeing Kasparov from the grip of the Soviet state. This set the stage for a more lasting set-back to FIDE's system when in 1993, Kasparov and challenger Nigel Short complained of corruption and a lack of professionalism within FIDE and split from FIDE to set up the Professional Chess Association (PCA), under whose auspices they held their match. The event was orchestrated largely by Raymond Keene, who has been at the centre of much off-the-board chess activity for a long time now. Keene brought the event to London (FIDE had planned it for Manchester), and England was whipped up into something of a chess fever: Channel Four broadcast some 81 programmes on the match, the BBC also had coverage, and Short appeared in television beer commercials. However, Kasparov crushed Short by five points, and interest in chess in the UK soon died down.
At the same time, FIDE held a championship match between Karpov (who had been champion before Kasparov) and Jan Timman (who had been defeated by Short in the Candidates final) in the Netherlands and Jakarta, Indonesia. Karpov emerged victorious. Ever since that time there have been two simultaneous World Champions and World Championships.
Kasparov went on to defend his PCA title against Viswanathan Anand, who had qualified through a series of events similar to those in the old FIDE system. It seemed his next challenger would be Alexei Shirov, who won a match against Vladimir Kramnik to apparently secure his place. However, plans for a match with Shirov never materialised, and he was subsequently omitted from negotiations, much to his disgust. Instead, Anand was lined up to play Kasparov once more, but here too, plans fell through (in somewhat disputed circumstances). Instead, Vladimir Kramnik was given the chance to play Kasparov in 2000. Against all expectations, Kramnik won.
FIDE, meanwhile, after one more traditional championship cycle which resulted in Karpov successfully defending his title against Gata Kamsky in 1996, largely scrapped the old system, instead having a large knock-out event in which a large number of players contested short matches against each other over just a few weeks. In the first of these events, champion Karpov was seeded straight into the final (as in previous championships), but subsequently the champion had to qualify like other players. Karpov defended his title in the first of these championships in 1998, but resigned his title in anger at the new rules in 1999. Alexander Khalifman took the title in 1999, Anand in 2000 and Ruslan Ponomariov in 2002.
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