In 1972 the Soviets played Canada in an exhibition series that saw the Soviet national team play a team composed of National Hockey League (NHL) players for the first time. Both the Olympics and World Championships did not allow professionals, so the best Canadian players were never able to compete against the Soviets, and in protest at this Canada had left international hockey in 1970. This series, known as the Summit Series, was a chance to see how the NHL players would fare.