Bobby Fischer's paranoia, obsessive behaviour and outrageous public statements have all but overshadowed his undoubted brilliance as a grandmaster.

In his heyday, Bobby Fischer was an American icon

The man who once said that "all I want to do, ever, is play chess" has played precious little of it at international level since he became world champion in 1972.

His remarkable defeat of Boris Spassky in the "chess match of the century" should have cemented his position at the very summit of the game, after a run of 20 consecutive tournament victories that is still hailed as the longest winning streak in world chess.

But instead of capitalising on his achievement, Fischer withdrew from competition. Three years later, the World Chess Federation stripped him of his title for failing to defend it against Anatoly Karpov.

Since then, apart from the Fischer-Spassky rematch in Yugoslavia in 1992 that provoked the wrath of the US government, America's greatest chess player has made headlines for all the wrong reasons.

His whereabouts have often been a mystery, but he apparently spent several years in central Europe before moving to Tokyo.

His reclusiveness, his anti-Semitic diatribes in radio interviews and - most unforgiveably for his fellow countrymen - his support for the 11 September 2001 attacks on the US have tarnished his legend.

"This is all wonderful news. It is time to finish off the US once and for all," he told a radio station in the Philippines after learning of the attacks.

Unreasonable

BBC journalist and chess expert David Edmonds, co-author of the book Bobby Fischer Goes To War, says Americans were profoundly shocked by the transformation.

"To many people, he had been an American icon in 1972. The match had been presented as a classic Cold War battle," he told BBC News Online.

Fischer (right) had a clean and logical chess-playing style

"The Soviet Union had held the world chess title since World War II and chess was an enormously important propaganda tool. Lenin was a keen chess player, so was Trotsky - even Karl Marx himself played chess.

"Bobby Fischer was held up as an archetype after that, and many people view what has happened to him with great sadness. They feel he has been letting not only himself down, but the US down as well."

Certainly Fischer's behaviour in recent years has been irrational to such an extent that many have questioned his sanity. He has repeatedly claimed that he is being hounded by a Jewish conspiracy, despite the fact that his mother was Jewish.

Even in his heyday, he was known for making unreasonable demands at tournaments, complaining about everything from the lighting of the hall to the amount of prize money on offer.

Ruthless

Fischer also had a gladiatorial view of chess. "I like the moment when I break a man's ego," he once said in an interview, adding to the sense of theatre surrounding him that helped elevate the game from an obscure pastime to worldwide front-page news.

"He did enjoy humiliating his opponents," says David Edmonds. "He could sense when his opponent was crumbling before him.

"But his style of playing was never flashy for the sake of showing off - it was clean, logical, ruthless and efficient. There was nothing ornamental about it.

"It was sometimes beautiful, elegant and harmonious, but he didn't try to please the crowds over the chessboard - he played to win the game."

Despite the scale of his downfall, Fischer has continued to inspire successive generations of chess players.

Many still see him as an artist with a unique charisma, and try to overlook the flaws that have brought him low.

But now that Fischer's violation of sanctions against Yugoslavia looks set to lead to a public trial, an endgame is looming that could destroy the last vestiges of his reputation.