Frunze became active in the Russian Social Democratic Labour Party (RSDLP). At the Second Congress of the RSDLP in London (1903), Vladimir Lenin and Julius Martov, the two main leaders, confronted each other in an ideological split over party tactics (Martov argued for a large party of activists, whilst Lenin wanted a small group of professional revolutionaries with a large fringe group of sympathisers). Frunze at the age of 18 sided with Lenin's majority, the so-called "Bolsheviks" ("majoritarians"), as opposed to Martov's minority, the "Mensheviks" (or "minoritarians").