From the second part of 1921 to 1922, Azerbaijan SSR used a red flag with the yellow Cyrillic characters АССР (ASSR). On March 12, 1920, the Azerbaijan SSR united with the Georgian SSR and the Armenian SSR under the Transcaucasian SFSR (TSFSR), that was split again into these three republics in 1936.
In 1937, golden hammer and sickle were added in the top left hand corner, with beneath the Latin characters AzSSR in a serif font in place of the Cyrillic characters. A third version was issued in 1940s, and had AzSSR substituted by its Cyrillic version АзССР. The last version of the flag was adopted by the Azerbaijan SSR on October 7, 1952. It was the flag of the Soviet Union, with an horizontal blue band on the bottom fourth.