Partly true. I should not have said "only" language, as that is clearly incorrect. Germans would have continued speaking their language in some settings, while also having to speak Russian in many settings as the preferred language. See, e.g.:
" During the Soviet times, the attitude to Ukrainian language and culture went through periods of promotion (policy of "
korenization", c. 1923 to c. 1933), suppression (during the subsequent period of
Stalinism), and renewed
Ukrainization (notably in the epoch of
Khrushchev, c. 1953 to 1964). Ukrainian cultural organizations, such as theatres or the
Writers' Union, were funded by the central administration.[
which?] While officially there was no
state language in the Soviet Union until 1990, Russian in practice had an implicitly privileged position as the only language widely spoken across the country. In 1990 Russian became legally the official all-Union language of the
Soviet Union, with constituent republics having rights to declare their own official languages.
[14][15] The Ukrainian language, despite official encouragement and government funding, like other regional languages, was often frowned upon or quietly discouraged, which led to a gradual decline in its usage. " (
https://en.wikipedia.org/wiki/Russi...ssion_and_fostering_of_the_Ukrainian_language)
I recall very well speaking with a Ukranian immigrant to the US who refused to utter a word in Russian, though she spoke it fluently, because she had been forced to learn it while living under the thumb of the empire.