anti-Stalinist left) led left-wing uprisings against the Bolsheviks. Such groups included Socialist Revolutionaries, Left Socialist Revolutionaries, Mensheviks and anarchists. Within this left-wing discontent, the most large-scale events were the Kronstadt rebellion and the Makhnovist movement. The Second International and the Two-and-a-Half International The International Socialist Commission (ISC, also known as Berne International) was formed in February 1919 at a meeting in Bern by parties that wanted to resurrect the Second International. Centrist socialist parties which did not want to be a part of the resurrected Second International (ISC) or Comintern formed the International Working Union of Socialist Parties (IWUSP, also known as Vienna International, Vienna Union, or Two-and-a-Half International) on 27 February 1921 at a conference in Vienna. The ISC and the IWUSP joined to form the Labour and Socialist International (LSI) in May 1923 at a meeting in Hamburg. From the Great Depression to the World War The 1920s and 1930s were marked by an increasing divergence between democratic and reformists socialists (mainly affiliated with the Labour and Socialist International) and revolutionary socialists (mainly affiliated with the Communist International), but also by tension within the Communist movement between the dominant Stalinists and dissidents such as Trotsky's followers in the Left Opposition. Trotsky's Fourth International was established in France in 1938 when Trotskyists argued that the Comintern or Third International had become irretrievably "lost to Stalinism" and thus incapable of leading the working class to power. Spanish Civil War In the Spanish Civil War (1936–1939), socialists (including the democratic socialist Spanish Socialist Workers' Party and the Marxist Workers' Party of Marxist Unification) participated on the Republican side, loyal to the left-leaning Popular Front government of the Second Spanish Republic, in alliance with anarchists of the communist and syndicalist variety and supported by the socialist Workers' General Union. The Spanish Revolution of 1936 was a workers' social revolution during the war, that is often seen as a model of socialism from below. An anarchist-inspired movement of peasants and workers, supported by armed militias, took control of Barcelona and of large areas of rural Spain where they collectivised the land. The Spanish Revolution was a workers' social revolution that began with the Spanish Civil War in 1936 and resulted in the widespread implementation of anarchist and more broadly libertarian socialist organisational principles in some areas for two to three years, primarily Catalonia, Aragon, Andalusia and parts of Levante. Much of Spain's economy