Yes, they did and all historians would agree that the Soviets did commit the massacre at Katyn.
The Katyn Forest massacre was when the Soviets brutally mudured about 25,000 Polish officers and civilians during World War II, around April 1940. Its significance wah that i was easier for communists to take the control over Poland and install a communistic government after the end of WWII.
The leadership of the US was not in the least suspicious; they had hard evidence that the Soviets were responsible for the 1940 mass-murders but chose to say the Germans did it as Stalin was then their ally.
Henri de Montfort has written: 'Le massacre de Katyn'
The Katyn massacre comes to mind immediately. Here is and excerpt on it from Wikipedia: The Katyn massacre, also known as the Katyn Forest massacre (Polish: zbrodnia katyńska, 'Katyń crime'), was a mass execution of Polish military officers, policemen and civilian prisoners of war ordered by Soviet authorities on March 5, 1940.[1][2] The number of victims is estimated at about 22,000, with the most commonly cited number of 21,768.[3] The victims were murdered in the Katyn forest in Russia, the Kalinin (Tver) and Kharkiv prisons and elsewhere.[4] About 8,000 were officers taken prisoner during the 1939 Soviet invasion of Poland, the rest being Poles arrested for allegedly being "intelligence agents, gendarmes, spies, saboteurs, landowners, factory owners, lawyers, priests, and officials."[3] Since Poland's conscription system required every unexempted university graduate to become a reserve officer,[5] the Soviets were able to round up much of the Polish intelligentsia, and the Jewish, Ukrainian, Georgian[6] and Belarusian intelligentsia of Polish citizenship.Interestingly, the Soviets tried to pin the blame for the massacre on the Germans during the IMT war crimes trials in Nurenburg after the war, much to the consternation of the English, Americans, and French. To avoid offending the Russians, who were also sitting in judgment of the Germans, they merely stated that the charge was 'not proved'. They knew all along that the Russians had done it, and russia finally admitted her guilt for the atrocity in 1990.
There was a massacre of Polish officers in the Katyn forest ~ see related link below .
Katyn war cemetery was created in 2000.
Louis Fitzgibbon has written: 'The Katyn memorial' -- subject(s): Katyn Memorial, London, London Katyn Memorial
http://www.electronicmuseum.ca/Poland-WW2/katyn_memorial_wall/kmw.html - possibly only confirmed victims. As long as the exact number of executed persons is not known, it is not possible to provide a full list.
The cast of Kraniet fra Katyn - 2006 includes: Lisbeth Jessen as Herself - Narrator
Katyn Slaughter and Silence - 1991 was released on: USA: 17 September 1991 (Chicago, Illinois)
Katyn Forest. The total number of Polish POWs murdered at Katyn was 22,000. The Russian government released the documents in May 2010.
Katyn - 2007 is rated/received certificates of: Argentina:16 Australia:MA Finland:K-15 Ireland:15A Japan:R15+ Singapore:NC-16 Sweden:15 UK:15