Following the Peterloo massacre of 1819, poet Percy Shelley wrote the political poem The Mask of Anarchy later that year, that begins with the images of what he thought to be the unjust forms of authority of his time—and then imagines the stirrings of a new form of social action. It is perhaps the first modern[vague] statement of the principle of nonviolent protest. A version was taken up by the author Henry David Thoreau in his essay Civil Disobedience, and later by Gandhi in his doctrine of Satyagraha. Gandhi's Satyagraha was partially influenced and inspired by Shelley's nonviolence in protest and political action. In particular, it is known that Gandhi would often quote Shelley's Masque of Anarchy to vast audiences during the campaign for a free India.