The International Workingmen's Association was an international group of socialists. Originally, it contained socialists of all kinds, including libertarian socialists (known by various names, including anarchists, anarcho-communists and Bakuninists) as well as the more authoritarian Marxists and social democrats.
First International
The Schism
The First International was split into two after Mikhail Bakunin, the foremost anarchist, and Karl Marx differed on both principles and practical courses of action.