may 20, 1963 - World Chess Championship 1963 Botvinnik vs Petrosian

Description:

At the World Chess Championship 1963, Tigran Petrosian narrowly qualified to challenge Mikhail Botvinnik for the World Chess Championship, and then won the match to become the ninth World Chess Champion.

The cycle is particularly remembered for the controversy surrounding the Candidates' Tournament at Curaçao in 1962, which resulted in FIDE changing the format of the Candidates Tournament to a series of knockout matches.