The USSR was comprised of 15 constituent republics - Russia, Ukraine, Belarus, Estonia, Latvia, Lithuania, Moldova, Georgia, Armenia, Azerbaijan, Turkmenistan, Kazakhstan, Uzbekistan, Tajikistan and Kyrgyzstan. While there were Russians living in practically every republic, most Russians lived in Russia with Ukraine having the second highest percentage of ethnic Russians. And while everyone in all 15 republics was "Soviet", onlu Russians called themselves "Russian." The terms "Russian" and "Soviet" because interchangeable in the West because Russia (Moscow) was the center of government and Russian was the official language (although many people didn't speak Russian outside of official circumstances.) Today Russian is still spoken in the former republics, but it's declining rapidly and being overtaken by the local languages.