In 1880, the German Social Democratic Party supported the call of its Belgian comrades, to call an international socialist congress in 1881. The little town of Chur was chosen and the Belgian socialists, the French Parti Ouvrier, the German social democracy, and the Swiss social democracy, participated in the preparations for the congress which would lead to the founding of the Socialist International.
Unlike the First, the Socialist International was made up of political parties with properly elected leaderships, political programs and membership bases in each country. The national sections of the International built trade unions, contested elections, and were deeply involved in the life of the working class in each country.
The outbreak of the Great War in 1914 and the national and revolutionary crises which the War engendered however, threw the International into crisis. A group of Social-Democrats, minorities within their own parties, met at Zimmerwald in 1915 to try to work out a joint platform of opposition to the slaughter taking place around them. The Zimmerwald Conference failed to unite all the Social Democrats or end the War, but did bring together a Left wing which supported the Russian Revolution and laid the basis for the Third (Communist) International.
5. September 1900 (Paris) Established a standing International Socialist Bureau composed of representatives of the socialist parties of all countries, its secretariat to be in Brussels. At this Congress, there was a split within the 28-strong Russian delegation. Lenin cast his vote for Plekhanov as the Russian delegate to the International, against Krichevsky, one of the editors of Rabocheye Dyelo.
In 1903, the Russian party split between Bolsheviks and Mensheviks.
See the Stenographic Record of the Second Congress of the RSDLP.