The first four chapters of Walter Benjamin's "The Work of Art in the Age of Mechanical Reproduction" relate to the changing social function of art and the loss of the aura in the age of changing reproduction technologies. As a Marxist, Benjamin view changes in art as indications of changes in the economical base of material power relations. This is why Benjamin employs the theory of dialectical materialism in "The Work of Art in the Age of Mechanical Reproduction" for the sake of analyzing the changes that art goes through in the 20th century.
Walter Benjamin describes the uses of new forms of art as a dialectic struggle between new forms of cultural production. He contradicts fascist uses of art to revolutionary uses of art through two aphorisms: the fascist tactics are characterized by the aestheticization of politics while the communist counter-reaction is characterized by the politicization of the aesthetics. Benjamin himself is of course all for the politicization of art and "The Work of Art in the Age of Mechanical Reproduction" is essentially an attempt to point to art's revolutionary potential.
An interesting point raised by Benjamin in "The Work of Art in the Age of Mechanical Reproduction" is the relations between capitalism and fascism. Capitalism and fascism meet at the point of alienation. Marx held that under capitalism the worker is alienated from his own products of work. In fascism this alienation is radicalized by the complete deletion of the individual function. The epitome of fascism according to Benjamin is the aestheticization of war which turns violence into an aesthetic product. This augments alienation since humanity can now joyfully witness its own destruction. People's alienation from their own products blinds them from seeing how these products bear their doom. The aestheticised war turns it away from the political realm into the realm of art where it can be consumed rather than discussed.