Only in 1991 after declassification of the archives was the truth established – some 20 thousand Polish officers had been murdered on orders of the Soviet government upon their occupation of Poland in 1939. Among the declassified documents were notes by [[Lavrenty Beria|Beria]], where it is stated that the People's Commissar of Internal Affairs ''de facto'' suggests to shoot ''"inveterate and incorrigible enemies of Soviet power"'': <blockquote>The [[NKVD]] of the [[USSR]] considers it necessary to propose to try the case of former Polish officers etc. located in the [[POW]] camps in separate proceedings by applying the highest level of punishment by shooting. The trying the case should be carried out without prompting arrestees and without announcing the formal indictment, the decision to terminate the investigation, and the final judgment.</blockquote>
The notes were signed by [[Stalin]], [[Vyacheslav Molotov|Molotov]], [[Kliment Voroshilov|Voroshilov]], Mikoyan and other Soviet leaders, all voted "for" the implementation of suggestion.<ref name="Rusarchives">{{cite web |title=Рассекречены подлинные документы по Катыни: Поляков расстреляли по приказу Сталина [Записка Берии, Постановление Политбюро И Другие Важнейшие Документы] (Declassified original documents on Katyn: Poles were shot on Stalin's orders [Beria's notes, Decision of the Politburo and other Important Documents]) |author=Елена Чинкова |date=April 28, 2010 |url=http://www.kp.ru/daily/24481/638132/|language=Russian}}</ref> According to Russian historians,<ref name="Russiapedia"/> the archives also contained a report dated 1946 from the then terminally ill Burdenko, in which he shared with his friend who had defected from the USSR, ''“Following the personal order of Stalin I went to Katyn where they had just excavated the graves. All bodies had been buried 4 years before. They died in 1940… For me, as a doctor, it was an obvious fact, which I couldn’t doubt. Our comrades from the NKVD [KGB predecessor] made a big mistake.”'' In November 2010 Russia's lower house of parliament (Duma) declared that the Soviet dictator and other Soviet officials had ordered the "Katyn crime" in 1940 and condemned Joseph Stalin by name for the mass execution of Poles at Katyn during World War II.<ref>{{cite web |title=Russian parliament condemns Stalin for Katyn massacre |publisher=BBC News Europe |date=26 November 2010 |url=httphttps://www.bbc.co.uk/news/world-europe-11845315 |accessdate=March 9, 2014}}</ref>
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