It's most commonly knowledge of the dark side of your superior who has greater favour with the commissariat.
Many people in aerospace spent time in the gulag before being "rehabilitated" out of necessity to support the Great Patriotic War and the space program.
Google and Wikipedia are your friends. It's all there.
Part of the problem dealing with the German invasion was that Stalin had purged close to half of the officer corps of the Red Army. Some of the ones lucky enough to be in the Gulag were hastily"Rehabilitated".
Grizz