The Socialist Republican Union (, USR) was a political party in France founded in 1935 during the late Third Republic which united the right-wing of the French Section of the Workers' International with the left-wing of the Radical republican movement. Prehistory: Socialist Republicanism The USR was founded on 3 November 1935 as a fusion of three small parties situated between the Marxist-socialist SFIO and the Radical PRRRS. It represented the consolidation into one single party of a particular political current that had been present in France since the 1890s: Socialist Republicanism. In late nineteenth-century France, formal political parties structured were virtually non-existent, except as informal parliamentary caucuses. Instead, each locality had its own socialist and/or republican club or committee, loosely grouped into federations. From 1900 these loose associations began to build a more formal structure, starting with the progressive centre-left Radical-Socialist Party (PRRRS, founded 1901) and the unified socialist party (SFIO), founded 1905). This forced left-wing republicans to decide whether to enter one or the other party. Many declined, rejecting the parliamentary-party discipline required: those right-wing Radicals who refused now labelled themselves the 'Independent Radicals' and sat in parliament in the very loose Radical Left group; from 1907, those right-wing socialists and left-wing Radicals who rejected strict party discipline called themselves 'Independent Socialists' and sat in parliament under the banner of 'Socialist Republicans', between the SFIO and PRRRS. The Socialist Republicans were highly diverse in their particular opinions, precisely as they did not possess a structured mass party but instead were a collection of independents and small local parties. However, they shared a belief in social reformism that connected them to the right wing of the SFIO, and a belief in the absolute legitimacy of parliamentary sovereignty, which connected them to the Radical-Socialists. As such, they often acted as a bridge between these two larger left-wing parties. Several of France's leading socialist and republican figures of the early 20th century originally belonged to this current: Jean Jaurès (who went on to become the chief figure of the French socialist Party); René Viviani and Aristide Briand (both heads of government around the time of the first world war); Alexandre Millerand (head of state after the war). Some socialist-republicans, such as Jaurès, ended up drifting to Marxism; others, like Millerand, to a Jacobin-inspired right-wing nationalism: it was never a coherent body of thought, but a catch-all grouping for all those who did