Tigran Vartanovich Petrosian (Russian: Тигран Вартанович Петросян; Armenian: Տիգրան Պետրոսյան; June 17, 1929 – August 13, 1984) was a Soviet Armenian Grandmaster, and World Chess Champion from 1963 to 1969. He was nicknamed "Iron Tigran" due to his almost impenetrable defensive playing style, which emphasised safety above all else.Petrosian was a Candidate for the World Championship on eight occasions (1953, 1956, 1959, 1962, 1971, 1974, 1977 and 1980). He won the World Championship in 1963 (against Mikhail Botvinnik), successfully defended it in 1966 (against Boris Spassky), and lost it in 1969 (to Spassky). Thus he was the defending World Champion or a World Championship Candidate in ten consecutive three-year cycles. He won the Soviet Championship four times (1959, 1961, 1969, and 1975). Petrosian is widely known for popularizing chess in Armenia. He was recognized as the hardest player to beat in the history of chess by the authors of a 2004 book.