Garry Kasparov's retirement at the age of 41 brings to an end 20 years of domination of the world of chess.
Those who meet Kasparov are struck by his intensity
In the black-and-white world of chess, Kasparov is regarded by many as the greatest.
There are those who are drawn to the flashes of brilliance of the eccentric former US world champion Bobby Fischer, but Kasparov's relentless two-decade crushing of the opposition has left most chess aficionados awed.
Like a Schumacher or a Sampras, the genius from Baku has an aura of invincibility that will live long in the memory.
He may have lost his championship to the younger Russian Vladimir Kramnik in 2000, but he is retiring as the undisputed world number one.
English grandmaster and Sunday Telegraph chess columnist Nigel Short is one of those who has been on the wrong end of Kasparov's brilliance, losing their world championship clash in 1993.
Speaking from his Athens home, he told BBC News that facing Kasparov across a chess board was a uniquely formidable prospect.
"He is one of the very few opponents I've been afraid to play. I can play a guy like [world number two Viswanathan] Anand and I respect him greatly, I've huge admiration, but I'm not afraid of him.
"I think [Kasparov's] greatest strength was the moves on the board but there was this physical presence when you played him, you felt this aggression.
"It is sad. In a way it is quite emotional. He is just a giant figure in chess. It is the passing of an era."
Much of the motivation for his retirement seems to stem from a desire to get away from the frustrating "politics" of world chess and spend more time with his real political interest, toppling Russian President Vladimir Putin.
When Kasparov spoke exclusively to the BBC News website on a trip to London in January, he was full of frustration at the cancellation of a championship match with Uzbek star Rustam Kasimdzhanov in Dubai.
He was candid about his disillusionment with efforts to organise a match with Kramnik, and about his feeling that he had achieved everything as a player and was now becoming a historian of the game.
He said: "I don't care. I no longer have the same passion for playing the world championship."
Nigel Short has been on the receiving end of Kasparov's genius
It is Kasparov's consistency, since his triumph over Anatoly Karpov in 1985 to claim the world championship, that marks him out as the greatest.
"Fischer stopped playing tournament chess at 29, Kasparov is 42 next month and he has gone on and he has won again and again and that is why he is really great," Short concluded.
"The Karpov match was an almighty struggle. He has more or less been on top ever since then, awesome."
Those who meet Kasparov are struck by his extraordinary energy and his intensity, and his play is equally affecting.
To Raymond Keene, English grandmaster and chess correspondent for the Times, Kasparov's play is "very dynamic, active, highly tactical and ambitious, clearly the best player the world has ever seen".
"Even in retirement many will still see him as the king across the water.
"The world champion is Kramnik, but he will never replace Kasparov."
And for Keene, Kasparov's writing on the game, and particularly his recent series on the world champions, My Great Predecessors, are a considerable achievement.
"His books on the previous champions are a milestone in chess writing. It is rather as if Michelangelo had produced a treatise on Da Vinci.
"You don't often get one great genius agreeing to evaluate the achievements of another."
Those looking back on Kasparov's career will see many guises, the young star setting himself against the Soviet establishment in the 1980s, the all-conquering champion, and the anti-Putin firebrand.
That he is a complex character, few doubt.
Chess writer and master Malcolm Pein said: "He is a man with a mission. He doesn't take kindly to people who waste his time or say things that don't make any sense. He uses every minute of the day.
"He is fed up with the world championship, with the idiots in charge of it."
And Short adds: "I've had ups and downs with Gary. At one time I didn't like him at all, he is a flawed character, but we all are.
"When he is doing things I think of him as a great genius but sometimes he behaves in an annoying or childish way. I very rarely have no opinion - I tend to have strong opinions for him or against him.
"When I saw him last he was very happy to chat and very affable, a familiar figure in a changing chess world."
Like retired boxers, always surrounded by rumours of a return, there will be many, not least Fide officials missing their most bankable star, who will long for Kasparov to change his mind.
But old adversary Short is not sure.
"I suspect that is it. But he is the greatest player of all time."