Complex sentence: On his release from prison Tsereteli joined the Social Democratic Labour Party (SDLP) and at the party's 1903 congress in London sided with Julius Martov against Lenin by becoming a Menshevik, opposed to Lenin's Bolsheviks.
Split into simpler sentences: On his release from prison Tsereteli joined the Social Democratic Labour Party (SDLP) and at the party's 1903 congress in London sided with Julius Martov against Lenin. By becoming a Menshevik, opposed to Lenin's Bolsheviks.