Both Abkhazia and other Georgian principalities were annexed into the Russian Empire in the nineteenth century, and remained part of it until the Russian Revolutions of 1917. While Georgia initially joined the Transcaucasian Democratic Federative Republic and subsequently became independent as the Democratic Republic of Georgia (DRG) in 1918, Abkhazia was initially controlled by a group of Bolsheviks, before ultimately joining the DRG, though its status was never clarified. In 1921 the Red Army invaded Abkhazia and Georgia, eventually incorporating them into the Transcaucasian Socialist Federative Soviet Republic. Initially Abkhazia was formed as an independent Soviet republic, the Socialist Soviet Republic of Abkhazia (SSR Abkhazia), though it was united with the Georgian Soviet Socialist Republic by a treaty; in 1931 the SSR Abkhazia was downgraded to an autonomous republic within the Georgian SSR, to much opposition from the Abkhaz.