World Chess Championship 1966
A World Chess Championship was played between Tigran Petrosian and Boris Spassky in Moscow from April 9 to June 9, 1966. Petrosian won.
1964 Interzonal Tournament
An interzonal tournament was held in Amsterdam in the Netherlands in May and June 1964. Six spots in the Candidates tournament were on the line.1965 Candidates matches
After the controversy surrounding the previous Candidates tournament, the 1965 tournament was the first to be played as a knock-out series of matches.Two players were seeded directly into the tournament: Mikhail Botvinnik and Paul Keres. Botvinnik declined, and his place was taken by Efim Geller, who finished 3rd in the 1962 Candidates.
Spassky won, earning the right to challenge champion Petrosian for the title.
Larsen and Geller played a third place playoff in Copenhagen, Denmark in March 1966. Larsen won 5–4.
1966 Championship match
The match was played as best of 24 games, with the champion retaining the title in the event of a 12–12 tie.While Petrosian retained the title with a 12–10 lead after Game 22, he and Spassky decided to play the final two games anyway.
This was the first World Chess Championship match since 1934 in which the reigning World Chess Champion defeated his opponent.
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