Poland has logded a protest. the answer:
1990 Mikhail Gorbachev admitted that the NKVD had executed the Poles and confirmed two other burial sites similar to the site at Katyn: Mednoye and Piatykhatky.
Watch this video. Eng sub
http://www.youtube.com/watch?v=QGr7eNmyPMY
Why do you say only about Katyn? And what do you say about the executions of soldiers of the Soviet Army in 1919? Why this silence?
http://www.strategic-culture.org/pview/2012/06/13/history-obscure-pages-plight-russian-soldiers-in-polish-captivity-ii.html
"At least two official accounts of the executions of captive Red Army servicemen are available. The fist one is found in the March 5, 1919 report compiled by the operative department (Department III) of the Polish army's supreme command, the second – in the report by the command of the Polish 5th army which said that around 400 Soviet Cossacks from the 3rd cavalry corps had been taken captive west of the Działdowo-Mława-Ciechanów line on August 24, 1920. According to the document, soldiers from the 49th infantry regiment of the Polish 5th army killed 200 of them by machine gun fire as a revenge for the deaths of 92 Polish soldiers and 7 officers. The reports by the Department II of the Polish supreme command did not reflect the fact."
https://en.wikipedia.org/wiki/Polish%E2%80%93Soviet_War
And 1939 Soviet Union returned back lost ground.
http://en.wikipedia.org/wiki/Curzon_Line