In 1900, Riazanov went into exile. The next year in Berlin Riazanov and his co-thinkers established a small Marxist group called "Borba" (Struggle), which attempted to unite the émigré Russian Marxists. Riazanov's group was excluded from the 2nd Congress of the Russian Social Democratic Labor Party that was held in London and Brussels in the summer of 1903. With the party divided between Bolshevik and Menshevik wings in the aftermath of this landmark convention, Riazanov and his co-thinkers pointedly declined to join either faction.