By the end of 1872, both Levski and Lyuben Karavelov, the chairman of the Bulgarian Revolutionary Central Committee (BRCC), which was situated in Bucharest, had figured out that the future success of the armed struggle against the Ottomans depended on the co-operation of both: external and internal committees.
There he also met Dmitry Pisarev and Lyuben Karavelov, who in the autumn of 1876 took part as a volunteer in the Serbian campaign against Turkey, and subsequently joined the Bulgarian irregular contingent with the Russian army in the war of 1877-1878.