Armenian forces eventually secured the region but their efforts were in vain when the Bolsheviks, successful in the Russian Civil War, pushed deep into the Caucasus. Syunik was one of the last major holdouts of the independent Armenian state whose leaders were eventually expelled by incoming Soviet authorities to Iran. During Sovietization, Syunik became part of Soviet Armenia, while the two other disputed territories, Nakhchivan and Nagorno-Karabakh became part of Soviet Azerbaijan. It then became part of Armenia under the Transcaucasian SFSR and part of the Armenian SSR in 1936. Under Soviet rule, Syunik suffered a devastating earthquake in April 1931, leaving 80% of its villages destroyed. A subsequent earthquake hit the region in May during the same year, destroying 27 of 38 villages in the Sisian district.