The Northern Caucasus was conquered by Russia after the Russo-Circassian War. Much of the Northern Caucasus seceded from Russia in March 1917 as the Mountainous Republic of the Northern Caucasus, taking advantage of the instability caused by the February Revolution and becoming a minor participant in the Russian Civil War. Mountainous Republic troops engaged in fierce clashes against the invading White General Anton Denikin's Volunteer Army, before the latter's defeat at the hands of the Red Army. The region was informally occupied by the Soviet Union shortly afterwards, and the republic was forced into accepting a nonviolent annexation in January 1921. It was reformed into the Mountainous ASSR, which was later dissolved in October 1924, replaced by a series of autonomous Okrugs and Oblasts.
