The flag of the Ukrainian Soviet Socialist Republic was adopted on March 10, 1919, to serve as the symbol of state of the Ukrainian SSR. Details of the official flag changed periodically before the break-up of the Soviet Union in 1991, but all were based on the red flag of the Bolshevik Revolution.
The first flag was red with the gold Cyrillic sans-serif letters У.С.С.Р. (USSR, acronym for Ukrayinskaya Sotsialisticheskaya Sovetskaya Respublika in the Russian language). In the 1930s, a gold border was added. In 1937, a new flag was adopted, with a small gold hammer and sickle added above the gold Cyrillic serif letters У.Р.С.Р. (URSR, for Ukrayins’ka Radyans’ka Sotsialistychna Respublika in the Ukrainian language).
The Soviet Union and two of its republics (Ukrainian SSR and Byelorussian SSR) were members of the United Nations (UN). Since all of their flags were red with only small markings in upper left corner, the UN demanded to change the flags in 1949.[1] To comply, the lettering was dropped and a blue stripe (⅓ of width) was added. It was adopted as the official flag of the Ukrainian SSR on November 21, 1949. The other republics of the Soviet Union soon followed the suit and customized the bottom third of their flags.[1]