One of the major scientific works of Franz Mehring, the first scientific biographer of Karl Marx and a prominent figure in the German and international labor movement, gives a biography of the founder of the communist movement Karl Marx and outlines the history of his development, together with his comrade-in-arms and friend F. Engels, of the proletarian worldview. The book also reflects the history of the creation and activities of the First International, whose inspirer and ideological leader was Marx.