Sometime after the arrival to his native land, he became acquainted with the chairman of a local Cheka Fruma Rostova (real name Khaikina) whom he married in the fall of 1918. Fruma in her early 20s was conducting so-called "cleaning" (zachistka) in the region, an ambiguous Cheka term. Simultaneously around that time, Shchors also was enrolled into the Russian Communist Party (bolshevik). In March–April, 1918 he commanded a joint detachment of Novozybkovsky district that fought against the Ukrainian Army and German army as a part of the 1st Insurgent Division. In September 1918 he formed the 1st Bohun Regiment and lead it against occupying German forces and the externally supported Ukrainian State army. In November 1918 he took command of the 2nd brigade of the 1st Ukrainian Soviet division (Bohun and Tarashcha regiments) and conquered Chernihiv, Kiev and Fastiv from the Ukrainian Directory. On February 5, 1919 Shchors was appointed mayor of Kiev.