ウクライナ人民共和国軍
In November 1918 Oskilko led an uprising against the hetman in Volyn. In December he was promoted to colonel of the Ukrainian People's Army. In January 1919 he became a General Khorunzhy (Major General) and a commander of the North group of the Ukrainian People's Army (around 40,000 soldiers). On January 5, 1919 his unit, which was passing through Berdichev, perpetrated a pogrom, killing 23 Jews. Oskilko participated in extinguishing the Bolshevik-led "Polissya Uprising" that was directed against the Directorate of Ukraine and preventing the advancement of the Polish army into Volyn. During that time Rivne became a temporary capital of Ukraine. Due to the strained situation in the region Oskilko suspected that the Ukrainian government and army became infiltrated by the Russian Cheka that sabotaged the frontlines of the Ukrainian army. He also did not trust Petlyura not because of his suspicions, but rather of his believe that Petlyura was weak in character and an unreliable person who became influenced by "generals-deserters".