The dead hand of Leftism

 According to Karl Marx, the Marxist revolution would be led by enlightened leaders, known as “the vanguard of the proletariat.” 

You will not find this phrase in any of his works.   Indeed, he stated quite the opposite:

'.. When the [First] International was formed we expressly formulated the battle-cry: the emancipation of the working classes must be conquered by the working classes themselves. We cannot therefore cooperate with people who say that the workers are too uneducated to emancipate themselves and must first be freed from above by philanthropic bourgeois and petty-bourgeois...'  (Karl Marx and Frederick Engels to Bebel, Liebknecht, Bracke, and Others, September 1879).