The article explores the little-studied period of the Civil War in the southern territories of Russia: the defense of Terek-Dagestan region from the advancing Soviet forces (mainly, by the Terek Cossack army) and subsequent retreat of the remaining part of the Southern Russian Armed Forces to the other side of the Caucasus Mountains. For his analysis, the author uses the historical and genetic method, referring to archive materials (from the State archive of the Russian Federation) and the participants’ memoirs. At the beginning of 1920, units of the Red army began a large-scale operation in the northern Caucasus aiming to destroy parts of the White army in Terek-Dagestan Region. The main part of the anti-Bolshevik forces in the region was made up of Terek Cossacks. For this reason the history of battles in the northern Caucasus at the beginning of 1920 is strongly connected with the history of the Terek Cossack army. The author analyzes battles at Terek in March, 1920, and reconstructs the evacuation of refugees from Vladikavkaz to Georgia. Also he discovers another way of evacuation — from Dagestan to Azerbaijan. The analysis demonstrates that in spite of retreat, the commanders of the army managed to preserve the Cossack units for subsequent anti-Bolshevik struggle.