It was founded in 1920, and consisted of six national federations (with a combined membership of about one million) at the time of its foundation.
However, the First World War put the build-up of an international workers' sport organisation on hold.
After the war two Belgians, Gaston Bridoux and Jules Devlieger, took initiative to revive the cooperation.
During the foundation, the French and Belgian delegations urged that the word 'Socialist' be omitted from the name of the organisation, in order to attract a broader following.
This policy was however challenged by the communists, which claimed that the workers' sport movement could not abstain from taking part in revolutionary struggle.
[5] The main activity of SASI was the organizing of the International Workers' Olympiads, portrayed as a socialist alternative to the 'bourgeois' Olympics.