Certain regions and periods of history were made unreliable for political reasons . Entire historical events could be erased , if they did not fit the party line . For example , until 1989 the Soviet leadership and historians , unlike their Western colleagues , had denied the existence of a secret protocol to the Soviet-German Molotov – Ribbentrop Pact of 1939 , and as a result the Soviet approach to the study of the Soviet-German relations before 1941 and the origins of World War II were remarkably flawed . In another example , the Soviet invasion of Poland in 1939 as well as the Polish-Soviet War of 1919 – 1920 were censored out or minimized in most publications , and research was suppressed , in order to enforce the policy of ' Polish-Soviet friendship ' . Similarly , the enforced collectivisation , the wholesale deportations or massacres of small nationalities in the Caucasus or the disappearance of the Crimean Tatars were not recognized as facts worthy of mention . Soviet historians also engaged in producing false claims and falsification of history ; for example Soviet historiography falsely claimed that the Katyn massacre was carried out by Germans rather than by Soviets . Yet another example is related to the case of Soviet reprisals against former Soviet POWs returning from Germany ; some of them were treated as traitors and imprisoned in Gulags for many years , yet that policy was denied or minimized by Soviet historians for decades and modern Western scholars have noted that " In the past , Soviet historians engaged for the most part in a disinformation campaign about the extent of the prisoner-of-war problem . " The Soviet interpretation of Marxism predetermined much of the research done by historians . Research by scholars in the USSR was limited to a large extent due to this predetermination . Some Soviet historians could not offer non-Marxist theoretical explanations for their interpretation of sources . This was true even when alternate theories had a greater explanatory power in relation to a historian 's reading of source material
Katyn massacre
Katyn massacre
Historiography in the Soviet Union