You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Civil_disobedience

Context:
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.

Question:
His poem is considered the first kind of what type of protest?

nonviolent