To further its goals, the BCP enlisted the support of the leftist in former Internal Macedonian-Adrianople Revolutionary Organization (IMARO), who espoused pro-Balkan Federation views. They changed their name to Macedonian Federative Organization (known as the "Federalists") and in 1918 outlined their policy in a manifesto. Its main points being the restoration of Macedonia to its original geographical boundaries. Their policy led them into open confrontation with the right-wing faction of the Internal Macedonian Revolutionary Organization (IMRO). At the Balkan Communist Conference in Vienna in May 1922, the Bulgarian delegate Vasil Kolarov first raised the issue of Macedonian and Thracian autonomy. Knowing the proposal was a threat to their countries borders, the Greek and Yugoslav delegates were unable to endorse it at this stage; however, in order for any chance of success, the communists needed the support of the IMRO. In June 1923, the IMRO collaborated with a nationalist military clique and overthrew the Bulgarian government. The government was condemned by the Communist International, as well as the absent communist resistance to it. When the communists did try to revolt during the September Uprising, they were quickly crushed by the government and its IMRO allies. The new premier, Alexandar Tsankov, released the imprisoned IMRO chiefs Todor Alexandrov and Alexander Protogerov who were arrested by the old regime as part of their IMRO crackdown agreement with Yugoslavia. During the spring of 1924, at the sixth conference of the BCP, they unveiled their Macedonian resolution, which stated that an autonomous Macedonia can “assure right and liberty to all its nationalities”, and hails the “Macedonian Revolutionary Organization, the real leader of the Macedonian slaves". Macedonian autonomy was portrayed in light of a class struggle of its inhabitants against the oppression of the middle class of the occupier countries, not an ethnic struggle.