In 1969 body-checking in all three zones in a rink was allowed, helmets and goaltender masks became mandatory in the early 1970s and in 1992 the IIHF began using the shootout.

Because of this, players from the National Hockey League (NHL) and its senior minor-league teams were not allowed to compete, while the Soviet Union was allowed to use permanent full-time players who were positioned as regular workers of an aircraft industry or tractor industry employer that sponsored what would be presented as an after-hours amateur social sports society team for their workers.

In the 2000s, the competition became more open as the "Big Six" teams[3] – Canada, the Czechia, Finland, Russia, Sweden, and the United States – have become more evenly matched.

[25][26] At the 1933 World Championships in Prague, Czechoslovakia, the United States won the gold medal, becoming the first non-Canadian team to win the competition.

Canada, represented by the East York Lyndhursts, was also undefeated and, in the final game of the tournament, the two teams met for the first time in international competition.

The game was so high profile in Canada that announcer Foster Hewitt flew to West Germany to provide play-by-play coverage.

[37] At the 1956 Winter Olympics in Cortina d'Ampezzo, Italy, Canada's Kitchener-Waterloo Dutchmen lost to both the Soviets and the United States in the medal round and won the bronze.

[14] At the 1960 Winter Olympics in Squaw Valley, California, Canada, the Soviet Union, Czechoslovakia and Sweden were the top four teams heading into the Games.

The Soviet Union won all seven of their games and the gold medal, but Canada finished the tournament with five wins and two losses, putting them in a three-way tie for second place with Sweden and Czechoslovakia.

Prior to 1964, the tie-breaking procedure was based on goal difference from games against teams in the medal round and under that system, Canada would have placed third ahead of the Czechoslovaks.

[44] In April 2005, the IIHF admitted that a mistake had occurred and announced that they had reviewed the decision and would award the 1964 Canadian team a World Championship bronze medal.

IOC president Avery Brundage was opposed to the idea of amateur and professional players competing together and said that ice hockey's status as an Olympic sport would be in jeopardy if the change was made.

[54] Led by goaltender Vladislav Tretiak and forwards Valeri Kharlamov, Alexander Yakushev, Vladimir Petrov and Boris Mikhailov, the Soviet Union won gold at the 1970 and 1971 World Championships and the 1972 Winter Olympics.

On the opening day of the tournament, Poland defeated the Soviet Union 6–4 thanks to a hat-trick from forward Wieslaw Jobczyk and the goaltending of Andrzej Tkacz.

At the beginning of the tournament, the roster of the West German team included Miroslav Sikora, a Polish-German forward who had previously played for Poland at the 1977 World Under-20 Championship.

At the time, players were not allowed to switch nationalities under any circumstances and the IIHF agreed to overturn the result and award the two points to Finland.

[68] Many of the Soviet Union's top players left, including the entire "Green Unit"–Larionov, Fetisov, Vladimir Krutov, Sergei Makarov and Alexei Kasatonov.

[73][74][75][76] Following this, the next decade was dominated by the so-called "Big Six"–Canada, the Czech Republic, Finland, Russia, Sweden and the United States.

[14] In 1994, the Canadian team finished the preliminary round undefeated and defeated Finland in the final to win their first World Championship since 1961.

Led by their top line of Saku Koivu, Ville Peltonen and Jere Lehtinen, the Finns defeated rival Sweden in the gold medal game.

In the mid-1990s, several new teams such as Slovakia, Latvia, Belarus, Kazakhstan and Ukraine were quickly improving and older nations such as Austria, France, Italy, Norway and Switzerland were at risk of being relegated to Pool B.

[85] At the 2003 World Championships, Sweden made one of the biggest comebacks in tournament history, rallying from a 5–1 deficit in their quarterfinal game against Finland to win 6–5.

IIHF president René Fasel responded that the tournament has television contracts and hosting commitments and that a large change would be difficult to put in place.

[96] The tournament was noted for having several surprising preliminary round results, including: Switzerland beating Canada for the first time in World Championship play;[97] Norway defeating eventual champions the Czech Republic;[98] and Denmark upsetting Finland and the United States en route to their first ever quarterfinal appearance.

[99] The German team, which had finished 15th in 2009 and only avoided relegation to Division I because they were set to host the 2010 tournament, advanced to the semi-finals for the first time since the new playoff format was adapted.

[104] The 2014 tournament was held for the first time in independent Belarus in spite of concerns of the human rights abuses perpetrated by the authoritarian government.

[22] Following the tournament, the IIHF held a congress and decided to adopt the "Canadian rules"–six men per side and three periods of play.

[122] The rule, which was first applied at the 1970 World Championships, was controversial: IIHF president Bunny Ahearne feared it would make ice hockey "a sport for goons.

The 1999 IIHF World Championship in Norway was a stark contrast to the finals the year before with many more goals scored and with end-to-end action – not defence – dominating play.

[132] However, the IIHF did agree to follow the NHL's league's zero-tolerance policy on obstruction and required referees to call more hooking, holding and interference penalties.