1980 IMO
In 1980, due to political sanctions resulting from the Soviet invasion of Afghanistan, there was no IMO. Many other international events, such as the Olympic Games, were also cancelled. However, a number of smaller replacement IMOs were held. These included the Austria-Poland Olympiad (which occurred annually anyway, having been established two years earlier), and the replacement olympiads in Mersch, Luxembourg; and Mariehamn, Finland. The olympiad at Mersch was attended by Belgium, Great Britain, the Netherlands, and Yugoslavia; in addition, France sent a team of four observers. The olympiad at Mariehamn was attended by Great Britain, Hungary, and Sweden.
