> you can declare any ethnicity at any time in Soviet Union. If you mean the official ethnicity that Soviet people had in their internal passports, this is str

> you can declare any ethnicity at any time in Soviet Union. If you mean the official ethnicity that Soviet people had in their internal passports, this is strictly false. The (in)famous Fifth Field has always been filled based on the parents' ethnicities. If both of one's parents were of one ethnicity (e.g. both are Tatars) then the child receives that ethnicity in their passport. If the parents belonged to two different ethnicities (e.g. a Russian mother and a Tatar father), the child was free to choose one of these two when receiving their first passport at the age of 16. See [1] (in Russian). [1]: https://ru.wikipedia.org/wiki/%D0%9F%D1%8F%D1%82%D0%B0%D1%8F_%D0%B3%D1%80%D0%B0%D1%84%D0%B0 https://ru.wikipedia.org/wiki/%D0%9F%D1%8F%D1%82%D0%B0%D1%8F...