Elections in the Soviet Union Wikipedia
The electoral system of the Soviet Union was based upon Chapter XI of the Constitution of the Soviet Union and by the Electoral Laws enacted in conformity with it. The Constitution and laws applied to elections in all Soviets, from the Supreme Soviets of the USSR, the Union republics and autonomous republics, through to regions, districts and towns. Voting was secret and direct via universal suffrage.
A 1945 decree allowed for members of the Red Army stationed outside the Soviet Union to vote for both chambers of the Supreme Soviet of the USSR (the Soviet of the Union and Soviet of Nationalities) in special 100,000-member districts. These were first enacted in the 1946 legislative elections and continued through the next decades as the Red Army continued its presence in the Eastern Bloc.