On the basis of an analysis of archival sources and the literature, the author addresses the combat operations of the Jezersko Detachment, commanded by Serbian Colonel Dobrosav Milenković, which played the main role in an offensive launched by the Kingdom of Serbs, Croats and Slovenes (the May-June Offensive) against the Austrian units in Carinthia in 1919. The Detachment was tasked with attacking from starting positions along the St. Leonhard–Bad Vellach–Trögernline and penetrating in the direction of Kühnsdorf–Völkermarkt. It had to maintain communication with the Ljubelj Detachment on its left flank and the Carinthian Detachment on its right flank. Together with other units of the Army of the Kingdom of Serbs, Croats and Slovenes, it successfully completed its battle path; Slovenian-Serbian units reached the river Gurk and occupied Zollfeld and Klagenfurt. The signing of a ceasefire resulted in the establishment of a demarcation zone, and the Paris Peace Conference ultimately decided that a plebiscite would determine which country Carinthia would fall under.