Kostetskyj began his literary career at this time authoring Russian-language reviews of theatrical performances; his first publication, signed with his pen name incorporating his mother's maiden name, was written in Vinnytsia in 1941. In the early 1940s, following the outbreak of the Second World War, he returned to German-occupied Vinnytsia and lived there until the autumn of 1942, when he was deported to Germany for forced labor. Kostetskyj continued an active literary career in the displaced persons camps after the war in West Germany, continuing to write and publish works in a combined traditional and modernist style, briefly publishing a short-lived artistic and literary journal, and becoming one of the founders of the Artistic Ukrainian Movement (MUR, Ukrainian: Мисте́цький Украї́нський Рух).