Kamenev joined the Social Democrats in 1901. He took a brief trip abroad in 1902, meeting Russian social democratic leaders living in exile, including Vladimir Lenin, whose adherent and close associate he became. He also visited Paris and met the "Iskra" group who published the newspaper. After attending the 3rd Congress of the Russian Social Democratic Labour Party (RSDLP) in London in March 1905, Kamenev returned to Russia to participate in the Russian Revolution of 1905 in St. Petersburg in October–December.