Complex sentence: In December 1921, left-leaning deserters formed the Macedonian Federative Organization, where Panitsa was active.The then Bulgarian premier Aleksandar Stamboliyski started then a campaign against the IMRO after his visit to Belgrade in May 1921.
Split into simpler sentences: In December 1921, left-leaning deserters formed the Macedonian Federative Organization, where Panitsa was active. The Bulgarian premier Aleksandar Stamboliyski started then a campaign against the IMRO after his visit to Belgrade in May 1921.