In 1956 FIDE introduced two apparently minor changes which Soviet grandmaster and chess official Yuri Averbakh alleged were instigated by the two Soviet representatives in FIDE, who were personal friends of reigning champion Mikhail Botvinnik. A defeated champion would have the right to a return match. FIDE also limited the number of players from the same country that could compete in the Candidates Tournament, on the grounds that it would reduce Soviet dominance of the tournament. Averbakh claimed that this was to Botvinnik's advantage as it reduced the number of Soviet players he might have to meet in the title match. Botvinnik lost to Vasily Smyslov in 1957 but won the return match in 1958, and lost to Mikhail Tal in 1960 but won the return match in 1961. Thus Smyslov and Tal each held the world title for a year, but Botvinnik was world champion for rest of the time from 1948 to 1963.