Socialist Party (France)
The Socialists suffered a severe split over participation in the wartime government of national unity. In 1919 the anti-war socialists were heavily defeated in elections. In 1920, during the Tours Congress, the majority and left wing of the party broke away and formed the French Section of the Communist International (Section française de l'Internationale Communiste or SFIC). This party joined the Third International, that was  founded by Lenin. The right wing, led by Léon Blum, kept the "old house" and remained in the SFIO.