During the 1930s, there were significant numbers of ethnic minorities living within the Ukrainian SSR. National Districts were formed as separate territorial-administrative units within higher-level provincial authorities. Districts were established for the republic's three largest minority groups, which were the Jews, Russians, and Poles. Other ethnic groups, however, were allowed to petition the government for their own national autonomy. In 1924 on the territory of Ukrainian SSR was formed the Moldavian Autonomous Soviet Socialist Republic. Upon the 1940 conquest of Bessarabia and Bukovina by Soviet troops the Moldavian ASSR was passed to the newly formed Moldavian Soviet Socialist Republic, while Budzhak and Bukovina were secured by the Ukrainian SSR. Following the creation of the Ukrainian SSR significant numbers of ethnic Ukrainians found themselves living outside the Ukrainian SSR. In 1920s the Ukrainian SSR was forced to cede several territories to Russia in Severia, Sloboda Ukraine and Azov littoral including such cities like Belgorod, Taganrog and Starodub. In the 1920s the administration of the Ukrainian SSR insisted in vain on reviewing the border between the Ukrainian Soviet Republics and the Russian Soviet Republic based on the 1926 First All-Union Census of the Soviet Union that showed that 4.5 millions of Ukrainians were living on Russian territories bordering Ukraine. A forced end to Ukrainisation in southern Russian Soviet Republic led to a massive decline of reported Ukrainians in these regions in the 1937 Soviet Census.