On May Day, 1937, Emma Goldman spoke in Hyde Park in London about anarchists in the Spanish Civil War, displaying a massive banner supporting the CNT.
In Catalonia, between May 3 and 8, in what came to be known as the May Days, clashes erupted in Barcelona between anarchists and other grassroots participants in the Spanish revolution, on one side, and on the other, police, communist party members serving Stalin, and other members of the Republican government. This presaged the defeat of the Spanish revolution at the hands of Franco, betrayed by authoritarians within its ranks.
https://libcom.org/article/may-days-barcelona-1937
