Ejército Negro
On September 1, Belash participated in the All-Army Congress of the Makhnovists, where he was elected chief of staff of the Revolutionary Insurrectionary Army of Ukraine (RIAU) and a member of the Military Revolutionary Council. He was one of the leaders of the RIAU during the battles near Uman in September 1919, which led to the complete destruction of several white regiments. After Uman, the RIAU launched a rapid attack on Yekaterinoslav. At the initiative of Belash, several detachments were sent out of the army for guerrilla operations and organization of uprisings in the Kherson, Kiev, Poltava and Chernihiv provinces.