It has its origin in the expelled Internationalist Bolshevik Faction of the Movement for Socialism (MAS). MAS was the Argentine section of the
International Workers League (IWL-FI). The Internationalist Bolshevik Faction regarded itself initially as an "external fraction" of the MAS/IWL-FI who had been wrongly expelled, and demanded the overturning of its expulsion. The Internationalist Bolshevik Faction became the
Socialist Workers' Party (PTS) in 1988. In 1989 the
Partido Obrero Socialista (POS) in Mexico, later renamed
Liga de Trabajadores Socialistas (LTS), was also expelled from the IWL-FI. The PTS and the POS founded the
Internationalist Faction of the IWL-FI (IFIWL-FI) in 1989. From 1988 to 1990 the PTS had three splits: first when a number of militants returned to the Argentinian
Movement for Socialism (MAS) party, then when another group of militants sympathized with the British
Workers Revolutionary Party (Worker Press) and the third when supporters of León Pérez (former member of the International Secretariat of the IWL-FI) decided to follow a mass party perspective (as opposed to a vanguard party). These splits forced the PTS to make a balance and self-criticism. This resulted in a further development. The PTS and the IFIWL-FI questioned the "update" of the
Transitional Program that
Nahuel Moreno, the leader of the IWL-FI, had made (his so-called theory of "Democratic Revolution"). The PTS and the IFIWL-FI regarded Moreno's update as an "anti-Trotskyist revision" of
Leon Trotsky's Theory of
Permanent Revolution. The PTS and the IFIWL-FI broke with Moreno's political tradition/heritage, ideology (termed Morenoism) and tendency (the IWL-FI). The IFIWL-FI was renamed
Internationalist Faction. In 1996 the
Trotskyist Fraction - International Strategy was founded. By 2004 it consisted of the Estratégia Revolucionaria, current name
Movimento Revolucionário de Trabalhadores (MRT), of Brazil and the Clase contra Clase, current name
Partido de Trabajadores Revolucionarios (PTR), of Chile as well as some militant sympathizers in Europe. In 2004, in its second international conference, the
Trotskyist Fraction - International Strategy decided to change its name to
Trotskyist Fraction - Fourth International (TF-FI). Following the economic crisis and demonstrations in several countries, the TF-FI grew in Latin America and Europe, and its manifesto of 2013 called for the formation of a new grouping: An International Movement for a Socialist Revolution - Fourth International. The manifesto was updated in 2021, due to new developments in the international arena. ==National sections==