He went back to London to attend the 5th RSDLP Party Congress, where he was elected to the party's Central Committee and the Bolshevik Center, in May 1907, but was arrested upon his return to Russia. After Kamenev was released from prison in 1908, he and his family went abroad later in the year to help Lenin edit the Bolshevik magazine "Proletariy." After Lenin's split with another senior Bolshevik leader, Alexander Bogdanov, in mid-1908, Kamenev and Grigory Zinoviev became Lenin's main assistants abroad. They helped him expel Bogdanov and his Otzovist (Recallist) followers from the Bolshevik faction of the RSDLP in mid-1909.