Ice hockey tournaments have been staged at the Olympic Games since 1920. The men's tournament was introduced at the 1920 Summer Olympics and was transferred permanently to the Winter Olympic Games program in 1924, in France. The women's tournament was first held at the 1998 Winter Olympics. The Olympic Games were originally intended for amateur athletes. However, the advent of the state-sponsored "full-time amateur athlete" of the Eastern Bloc countries further eroded the ideology of the pure amateur, as it put the self-financed amateurs of the Western countries at a disadvantage. The Soviet Union entered teams of athletes who were all nominally students, soldiers, or working in a profession, but many of whom were in reality paid by the state to train on a full-time basis. In 1986, the International Olympic Committee (IOC) voted to allow professional athletes to compete in the Olympic Games starting in 1988. The National Hockey League (NHL) was initially reluctant to allow its players to compete because the Olympics are held in the middle of the NHL season, and the league would have to halt play if many of its players participated. Eventually, NHL players were admitted starting in 1998. From 1924 to 1988, the tournament started with a round-robin series of games and ended with the medal round. Medals were awarded based on points accumulated during that round. In 1992, the playoffs were introduced for the first time since 1920. In 1998, the format of the tournament was adjusted to accommodate the NHL schedule; a preliminary round was played without NHL players or the top six teams—Canada, the Czech Republic, Finland, Russia, Sweden and the United States—followed by a final round which included them. The tournament format was changed again in 2006; every team played five preliminary games with the full use of NHL players. The games of the tournament follow the rules of the International Ice Hockey Federation (IIHF), which differ slightly from the rules used in the NHL. In the men's tournament, Canada was the most successful team of the first three decades, winning six of seven gold medals from 1924 to 1952. Czechoslovakia, Sweden and the United States were also competitive during this period and won multiple medals. Between 1920 and 1968, the Olympic hockey tournament was also counted as the Ice Hockey World Championship for that year. The Soviet Union first participated in 1956 and overtook Canada as the dominant