The organization was involved, from the outset, in social struggles around the country, working on the strengthening of trade unions and advancing towards workers' unity.

Opposed to electoral participation, they advocated abstention in the 1971 general election, refusing to support the Broad Front.

In 1975, activists of the FAU, the ROE and the OPR-33 in exile in Buenos Aires (Hugo Cores, Gerardo Gatti and Léon Duarte) founded the People's Victory Party (Spanish: Partido por la Victoria del Pueblo, PVP), a Libertarian Marxist group sympathetic to the Cuban Revolution.

[4][5] Cornered by the repression of Uruguayan and Argentine special services, about fifty FAU members were tortured, killed and disappeared, while others were sentenced to long years in prison.

They also run a printing press, 6 community radio stations, 4 athenaeums, 3 libraries and built a Solidarity and Mutual Support Space.