Answer
Boris Spassky defeated Tigran Petrosian in 1969 to become the world champion. The match was held in Moscow and Spassky won by a score of 12.5-8.5. This was the first time that the world championship had been held in the Soviet Union. Spassky was the first Soviet player to win the world championship and he held the title until 1972, when he lost to Bobby Fischer.