Sectarianism
Sectarianism is a form of opportunist conduct in which revolutionary movements split and otherwise oppose each other despite sharing common interests in socialist revolution. Calls against sectarianism date as far back as the the Communist Manifesto, in which it is stated "the Communists do not form a separate party opposed to the other working-class parties."
Sectarianism is distinct from communist opposition to revisionist and opportunist trends in the working class movement, examples of which being the split with the anarchists in the First International, Albanian–Soviet split, and Sino-Albanian Split.