Korchnoi played three matches against Anatoly Karpov, the latter two for the World Chess Championship. In 1974, he lost the Candidates final to Karpov by the narrowest margin: 11.5–12.5. Karpov was declared world champion in 1975 when Bobby Fischer failed to defend his title. Then, after defecting from the Soviet Union in 1976, Korchnoi won two Candidates cycles to qualify for World Championship matches with Karpov in 1978 and 1981.