After more conflict, the Byelorussian Soviet Socialist Republic was declared in 1920. With the defeat of Ukraine in the Polish-Ukrainian War, after the March 1921 Peace of Riga following the Polish-Soviet War, central and eastern Ukraine were annexed into the Soviet Union as the Ukrainian Soviet Socialist Republic. In 1922, the Russian SFSR, Ukraine SSR, Byelorussian SSR and Transcaucasian SFSR were officially merged as republics creating the Union of Soviet Socialist Republics, or Soviet Union.