Bobby Fischer's modest grave in Iceland

In his heyday, Bobby Fischer was an American icon

His surprise defeat of Soviet champion Boris Spassky in 1972 in the "chess match of the century" established him at the top 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 win, he withdrew from competition and rarely played at international level afterwards.

In recent years, he had been better known for his paranoia, obsessive behaviour and outrageous public statements, which all but overshadowed his undoubted brilliance.

Volatile and impetuous

Born in Chicago in 1943, Bobby Fischer was a chess genius from the beginning, playing from the age of eight.

He was US junior champion at 13 and open champion at 14, a title he won seven more times.

He became a grandmaster at 15, but was already showing himself to be volatile and impetuous, often turning up late for or walking out of matches.

His victory in 1972 was unexpected, as every world champion since World War II had been from the USSR, and seemed a foretaste of a promising career.

But the man who once said that "all I want to do, ever, is play chess" played precious little of it at international level after he won the world championship in Reykjavik in 1972.

Instead of capitalising on his win, 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 made headlines for all the wrong reasons.

Reclusive

Until Fischer was detained in July 2004 while trying to leave Japan with a revoked US passport, his whereabouts had often been a mystery.

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

The former grandmaster did not age well

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 the BBC News website.

"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 later years was irrational to such an extent that many questioned his sanity. He repeatedly claimed that he was 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.

Fischer (right) was a gladiator of the chessboard

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

"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," he says.

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

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

Until the end, the US government viewed him as a fugitive from justice - but his move to Iceland meant he escaped the endgame of a public trial that could have destroyed the last vestiges of his reputation.