Internationalism is a core component of emancipatory theory and practice. At the same time, it has always been controversial and has gone through various conjunctures characterized by very different forms of mobilization and organization. At the latest since the founding of the International Workingmen's Association (IWA) in 1864, or the First International for short, internationalism has been a political and organizational claim and at the same time a theoretical challenge for the emancipatory left. Internationalism was and is a left-wing perspective that seeks to unite anti-capitalist and anti-fascist, anti-colonial, anti-racist and anti-patriarchal claims. But internationalism does not have a uniform concept, it always exists in a plural: authoritarian and party-oriented, anti-authoritarian and association-oriented strategies, liberation nationalist and transnationalist approaches exist side by side and sometimes fight each other.
Internationalist practice has experienced various conjunctures, from the Paris Commune of 1871 to the Spanish Civil War (1936-1939), from decolonization and the revolts of the '1968s' to the feminist awakening, the solidarity movements of the 1970s and 1980s, the Zapatista uprising of 1994 and the anti-globalization movements around 2000 to the debates on a 'new internationalism' in the present day.