Babij graduated from a high school in Tarnopol, then studied classical philology at the Jan Kazimierz University in Lwów. Following the start of World War I in 1914 he was called into the Austro-Hungarian Army, where he served in the Ukrainian Sich Riflemen. In 1918-1919 he fought against Poland in the Ukrainian Galician Army and in 1920 participated as an officer of the Ukrainian People's Army in the Kyiv Offensive of the joint Polish-Ukrainian forces.