Liberal Union (Italy) in the context of "Political alliance"

The Italian Socialist Party (Italian: Partito Socialista Italiano, PSI) was a social democratic and democratic socialist political party in Italy, whose history stretched for longer than a century, making it one of the longest-living parties of the country. Founded in Genoa in 1892, the PSI was from the beginning a big tent of Italy's political left and socialism, ranging from the revolutionary socialism of Andrea Costa to the Marxist-inspired reformist socialism of Filippo Turati and the anarchism of Anna Kuliscioff. Under Turati's leadership, the party was a frequent ally of the Italian Republican Party and the Italian Radical Party at the parliamentary level, while lately entering in dialogue with the remnants of the Historical Left and the Liberal Union during Giovanni Giolitti's governments to ensure representation for the labour movement and the working class. In the 1900s and 1910s, the PSI achieved significant electoral success, becoming Italy's first party in 1919 and during the country's Biennio Rosso in 1921, when it was victim of violent paramilitary activities from the far right, and was not able to move the country in the revolutionary direction it wanted.

A split with what became known as the Communist Party of Italy and the rise to power of former party member and Italian fascist leader Benito Mussolini, who was expelled from the party, class struggle and internationalism in favour of corporatism and ultranationalism, and his National Fascist Party led to the PSI's collapse in the controversial 1924 Italian general election and eventual ban in 1925. This led the party and its remaining leaders to the underground or in exile. The PSI dominated the Italian left until after World War II, when it was eclipsed in status by the Italian Communist Party (PCI). The two parties formed an alliance lasting until 1956 and governed together at the local level, particularly in some big cities and the so-called red regions until the 1990s. The PSI suffered the right-wing split of the Italian Democratic Socialist Party, whose members opposed the alliance with the PCI and favoured joining the Centrism coalition, in 1947 and the left-wing split of the Italian Socialist Party of Proletarian Unity, whose members wanted to continue the cooperation with the PCI, in 1964. Starting from the 1960s, the PSI frequently participated in coalition governments led by Christian Democracy, from the Organic centre-left to the Pentapartito in the 1980s.