First Nagorno-Karabakh War
In 1918, after the World War I as well as the collapse of the Ottoman Empire, Armenia and Azerbaijan became independent, both of which claimed Nagorno-Karabakh. Consequently, the region was admitted as territory of the Azerbaijan Democratic Republic of 1918-1920 at the Versailles Peace Conference. In the early 1920s, the South Caucasus countries got annexed by the Soviet Union, whose Caucasus Bureau of the Central Committee of the Russian Communist Party of the Bolsheviks made Nagorno-Karabakh remain under the Azerbaijan Soviet Socialist Republic. In 1923, the region was accorded the autonomous status as the Nagorno-Karabakh Autonomous Oblast.