In 1904, at the age of sixteen, Doletsky joined the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL), a party led by Rosa Luxemburg and Jan Tyszka.
In 1912, he supported the 'rozlamovist' group within the party who opposed Tyszka's leadership style and who were allied with Vladimir Lenin and the Bolsheviks.
He represented the group at the abortive 'unification' conference in Brussels in July 1914, which was supposed to reunite the separate factions of the Russian Social Democratic Labour Party and the SDPKiL.
[3] Eugene Lyons, who worked for TASS in the US and regularly corresponded with Doletsky, was disillusioned on meeting in Moscow in 1928: At the far end of a long room stood a vast and shiny desk covered with many telephones and push buttons, and behind its imposing expanse sat a bearded, obese little man, blinking behind thick glasses.
"[4]Alexander Barmine saw Doletsky, whom he described as a "conscientious official and the kind of man who never got involved in political quarrels", and Deputy People's Commissar for Foreign Affairs, Nikolai Krestinsky, on two occasions early in 1937: "On the first occasion they were still both normal men, preoccupied naturally, but capable of smiling, joking, making plans, giving advice.