IMRO followed by starting an insurgent war in Vardar Macedonia, together with Macedonian Youth Secret Revolutionary Organization, which also conducted guerrilla attacks against the Serbian administrative and army officials there. In 1923 in Stip, a paramilitary organisation called Association against Bulgarian Bandits was formed by Serbian chetniks, IMRO renegades and Macedonian Federative Organization (MFO) members to oppose IMRO and MMTRO. On 9 October 1934 IMRO member Vlado Chernozemski assassinated Alexander I of Yugoslavia.