Cubism:

It was against this background of public anger that Jean Metzinger and Albert Gleizes wrote Du "Cubisme" (published by Eugène Figuière in 1912, translated to English and Russian in 1913). Among the works exhibited were Le Fauconnier's vast composition Les Montagnards attaqués par des ours (Mountaineers Attacked by Bears) now at Rhode Island School of Design Museum, Joseph Csaky's Deux Femme, Two Women (a sculpture now lost), in addition to the highly abstract paintings by Kupka, Amorpha (The National Gallery, Prague), and Picabia, La Source, The Spring (Museum of Modern Art, New York).

Please answer a question about this article. If the question is unanswerable, say "unanswerable".  What did Metzinger and Gleizes write Du "Cubsime" in support of?
unanswerable