[8] He also published an ethnographic study of Macedonia's population, which he described as consisting of Bulgarians, Turks, Albanians, Vlachs (Aromanians and Megleno-Romanians), Jews and Gypsies.

He did not approve of the untimely outbreak of the Uprising on Ilinden,[3] August 2, 1903, but he participated as the leader of a cheta (armed band),[8] of which Aromanian revolutionary Ioryi Mucitano was part.

After the Young Turks Revolution of 1908, Petrov together with writer Anton Strashimirov edited the "Kulturno Edinstvo" magazine ("Cultural Unity"), published in Thessaloniki (Solun).

[13] At the end of the war he was one of the initiators of the formation of a new leftist organization called Provisional representation of the former United Internal Revolutionary Organization, and this government set a task of defending the positions of the Macedonian Bulgarians by agitating for a creation of independent Macedonia at the Paris Peace Conference (1919–1920).

[15] BANU rejected territorial expansion and aimed at forming a Balkan federation of agrarian states, a policy which began with a détente with Yugoslavia.

Then Petrov had to deal with the problem of Bulgarian refugees who had to leave Yugoslavia and Greece, thus incurring IMRO rightist faction leaders' hatred upon himself.

[7][21] The assassination of Gyorche Petrov complicated relations between IMRO and the Bulgarian government and produced significant dissensions in the Macedonian movement.