The Russian NGO Memorial has pledged to pursue all legal means to get Moscow to recognize Soviet responsibility for the deaths of over 20,000 Polish officers in the Katyn massacre of 1940.
This is a turn up for the (history) books. A group of Russians are fighting to get Putin and others to face up to Soviet war crimes.
So far, Moscow has failed to acknowledge the extent of the crime, even though the rest of the world thinks it's self evident.
And in March, 2006, Moscow informed the Polish government that they would not recognize the massacre as an act of political repression.
In April and May 1940, the Soviet secret police (NKVD) executed over 20,000 Polish officers and policemen imprisoned in camps Kozyelsk, Ostashkov and Starobelsk as well as Poles imprisoned in the Western regions of Belarus and Ukraine.
See Memorial NGO web site here.