In the beginning of the 1905 Russian revolution he returned to Russia. He worked among workers of Dvinsk, Bialystok, Gomel, was one of the leaders of the strike at Libava-Romny railroad. At the 7-th Congress of the Bund, where he first used the pseudonym Max Goldfarb, he was elected a candidate for the Central Committee. At the end of 1906 he was arrested by police and spent three months in prison. After that he left Russia - first to England where he participated at the London 5th Congress of the Russian Social Democratic Labour Party, and then to Brussels, where in 1912 he graduated from the Free University of Brussels with a Ph.D. in Economic Sciences (his supervisor was Emile Vandervelde - the future Minister of State of Belgium).