After playing in the 1962 Interzonal in Stockholm, Petrosian qualified for the Candidates Tournament in Curaçao along with Pal Benko, Miroslav Filip, Bobby Fischer, Efim Geller, Paul Keres, Viktor Korchnoi, and Mikhail Tal.
Petrosian, representing the Soviet Union, won the tournament with a final score of 17½ points, followed by fellow Soviets Geller and Keres each with 17 points and the American Fischer with 14.
Fischer later accused the Soviet players of arranging draws and having "ganged up" on him to prevent him from winning the tournament.
As evidence for this claim, he noted that all 12 games played between Petrosian, Geller, and Keres were draws.
Statisticians pointed out that when playing against each other, these Soviet competitors averaged 19 moves per game, as opposed to 39.5 moves when playing against other competitors.
Although responses to Fischer's allegations were mixed, FIDE later adjusted the rules and format to try to prevent future collusion in the Candidates matches.

Having won the Candidates Tournament, Petrosian earned the right to challenge Mikhail Botvinnik for the title of World Chess Champion in a 24-game match.
In addition to practicing his chess, Petrosian also prepared for the match by skiing for several hours each day.
He believed that in such a long match, physical fitness could become a factor in the later games.
This advantage was increased by Botvinnik being much older than Petrosian.
Whereas a multitude of draws in tournament play could prevent a player from taking first place, draws did not affect the outcome of a one-on-one match.
In this regard, Petrosian's cautious playing style was well-suited for match play, as he could simply wait for his opponent to make mistakes and then capitalize on them.
Petrosian won the match against Botvinnik with a final score of 5 to 2 with 15 draws, securing the title of World Champion.
After playing in the 1962 Interzonal in Stockholm, Petrosian qualified for the Candidates Tournament in Curaçao along with Pal Benko, Miroslav Filip, Bobby Fischer, Efim Geller, Paul Keres, Viktor Korchnoi, and Mikhail Tal. Petrosian, representing the Soviet Union, won the tournament with a final score of 17½ points, followed by fellow Soviets Geller and Keres each with 17 points and the American Fischer with 14. Fischer later accused the Soviet players of arranging draws and having "ganged up" on him to prevent him from winning the tournament. As evidence for this claim, he noted that all 12 games played between Petrosian, Geller, and Keres were draws. Statisticians pointed out that when playing against each other, these Soviet competitors averaged 19 moves per game, as opposed to 39.5 moves when playing against other competitors. Although responses to Fischer's allegations were mixed, FIDE later adjusted the rules and format to try to prevent future collusion in the Candidates matches.
Having won the Candidates Tournament, Petrosian earned the right to challenge Mikhail Botvinnik for the title of World Chess Champion in a 24-game match. In addition to practicing his chess, Petrosian also prepared for the match by skiing for several hours each day. He believed that in such a long match, physical fitness could become a factor in the later games. This advantage was increased by Botvinnik being much older than Petrosian. Whereas a multitude of draws in tournament play could prevent a player from taking first place, draws did not affect the outcome of a one-on-one match. In this regard, Petrosian's cautious playing style was well-suited for match play, as he could simply wait for his opponent to make mistakes and then capitalize on them. Petrosian won the match against Botvinnik with a final score of 5 to 2 with 15 draws, securing the title of World Champion.
Tigran Petrosian