That Napoleon was eventually defeated was the result - 
    in part - of a painting that depicted a giant, rather 
    inattentive, absent-minded giant eating a human corpse 
    like a candy bar.

If you are referring to Goya's "Saturn Devouring His Son" then I don't think it was even painted before Napoleon's defeat. In any case, suggesting Napoleon's defeat was "the result" of a painting is hyperbole to the point of absurdity. There are examples of art having significant impact in the world but this is not one.