There is a small population of Ainu living in far east of modern Russia. This can be probably extrapolated to them living there during USSR times. Ainu have ha

There is a small population of Ainu living in far east of modern Russia. This can be probably extrapolated to them living there during USSR times. Ainu have had... strained relationship with Japan, so they could had been enlisted by the USSR during the war to decrypt messages. That's not to say that Ainu people's relationship with USSR has been ideal either, but them serving as translators during the war seems plausible.