Hint 1
This player became World Champion in 1960, defeating a player who had held the title for many years.
Hint 2
He was famous for sacrificing material, often without being able to calculate every variation. He once said: "You must take your opponent into a deep dark forest where 2+2=5, and the path leading out is only wide enough for one."
Hint 3
His nickname was "The Magician from Riga."
Who is the grandmaster?