Among the Second International's famous actions were its 1889 declaration of 1 May (May Day) as International Workers' Day and its 1910 declaration of the International Women's Day, first celebrated on 19 March and then on 8 March after the main day of the women's marches in 1917 during the Russian Revolution. It initiated the international campaign for the eight-hour working day.
The International's permanent executive and information body was the International Socialist Bureau (ISB) based in Brussels and formed after the International's Paris Congress of 1900. Emile Vandervelde and Camille Huysmans of the Belgian Labour Party were its chair and secretary. Vladimir Lenin was a member from 1905.
The Second International dissolved in 1916 during World War I because the separate national parties that composed the International did not maintain a unified front against the war, instead generally supporting their respective nations' role. French Section of the Workers' International (SFIO) leader Jean Jaurès's assassination, a few days before the beginning of the war, symbolized the failure of the antimilitarist doctrine of the Second International. At the Zimmerwald Conference in 1915, anti-war socialists attempted to maintain international unity against the social patriotism of the social democratic leaders.
In 1920, the defunct Second International was reorganized. However, some European socialist parties refused to join the reorganized International and decided instead to form the International Working Union of Socialist Parties (IWUSP) (Second and a half International or Two-and-a-half International), heavily influenced by Austromarxism. In 1923, IWUSP and the Second International merged to form the social democratic Labour and Socialist International which continued to exist until 1940. After World War II, a new Socialist International was formed to continue the policies of the Labour and Socialist International and it continues to this day.
Another successor was the Third International organized in 1919 under the soon-to-be Communist Party of the Soviet Union. It was officially called the Communist International (Comintern) and lasted until 1943 when it was dissolved by then Soviet leader Joseph Stalin.
In Latin America, the International had two affiliates, namely the Socialist Party of Argentina and the Socialist Party of Uruguay.
The exclusion of anarchists
Anarchists tended to be excluded from the Second International, nevertheless "anarchism had in fact dominated the London Congress of the Second International". This exclusion received the criticism from anti-authoritarian socialists present at the meetings. It has been argued that at some point the Second International turned "into a battleground over the issue of libertarian versus authoritarian socialism. Not only did they effectively present themselves as champions of minority rights, they also provoked the German Marxists into demonstrating a dictatorial intolerance which was a factor in preventing the British labor movement from following the Marxist direction indicated by such leaders as Henry Hyndman.