 Complete the following phrase:  In September 1870, Nechayev published an issue of the Commune magazine in London as the Second French Empire of Napoleon III collapsed. Hiding from the Okhrana, he went underground in Paris and then in Zürich. He also kept in touch with the Polish Blanquists such as Caspar Turski and others. In September 1872, Karl Marx produced the threatening letter which Nechayev had written to the publisher at the 