Karl Marx co-authored "The Communist Manifesto" with Friedrich Engels. Published in 1848, this foundational text of Marxism laid out the principles of class struggle, the critique of capitalism, and the vision for a socialist future. Engels provided significant support to Marx during its creation and played a crucial role in further developing Marxist theory. Their collaboration highlighted the shared commitment to analyzing the socio-economic conditions of their time, advocating for the proletariat's upheaval against the capitalist class, and envisioning a society characterized by communal ownership and egalitarian principles.