Treaty of Moscow
Before joining the Soviet Union, the Democratic Republic of Armenia signed the Treaty of Alexandropol, on 3 December 1920, agreeing to the current border between the two countries, though the Armenian government had already collapsed due to a concurrent Soviet invasion on 2 December. Afterwards Armenia became an integral part of the Soviet Union. This border was ratified again with the Treaty of Moscow (1921), in which the Bolsheviks ceded the already Turkish-occupied provinces of Kars, Iğdır, Ardahan, and Artvin to Turkey in exchange for the Adjara region with its capital city of Batumi.