In 1924, the International Chess Federation (FIDE) was established. After the death of the fourth world champion Alexandre Alekhine in 1946, all subsequent world champions were decided by a qualification organized by FIDE.
Between 1948 and 1991, chess was dominated by Soviet sportsmen. After the collapse of the USSR, the system of identifying the strongest player was changed several times, but from 2008 onwards, the champion was decided by head-to-head matches.