Poland's acclaimed director Andrzej Wajda trained the bright light of cinema on Wednesday on one of his country's darkest episodes: that of the Soviet massacre of 22,500 Polish army officers and civilians in 1940.

For the 81-year-old director, the film "Katyn" -- presented in Warsaw and named after the forest where some of the slayings occurred -- is more than another of his deft political scrutinies: it's also very personal.

His father, Captain Jakub Wajda, was one of the victims who fell to the Soviet invaders, shot in the back of the head by Stalin's secret police.
His death, and his mother's refusal to accept it, forms the inspiration of "Katyn", Wajda explained at the press screening.

"My mother fed off illusions up to the end of her life, because my father's last name was given with a different first name on the list of massacred officers," the director said.

Wajda -- who won an honorary Oscar in 2000 for his lifetime's work, including such Polish classics as "Kanal" (1957), "Ziemia Obiecana" (1975) and Czlowiek z zelaza" (1981) -- said "Katyn" was to get its
public premiere on September 17, the date 68 years ago that the Red Army pushed its way into Poland, already half-occupied by the Nazis.

The movie starts on that fateful day in 1939 with two mobs pushing past each other: one to flee the Soviets, the others the Germans.

It ends with powerful and disturbing depictions of the executions in Katyn Forest. Thousands of Polish officers and civilians deemed "counterrevolutionaries" were killed.

The episode remained obscured for a long time, even after the Nazis revealed the existence of the mass graves in 1941 following the end of the German-Soviet pact after Nazi troops invaded the Soviet Union.

Moscow blamed the Germans for the massacre, and the West remained silent so as not to antagonise the Soviet Union, then a valuable ally in the fight against Hitler. In Communist Poland, the subject was taboo.

It was only in 1990 that then Soviet leader Mikhail Gorbachev admitted his country's responsibility.

Wajda stressed that "this film would not have seen the light of day" during Poland's Communist years.

"No sane-minded filmmaker would have been able to make this during the Communist era, unless it was to present an official version," he said.

"I hope there will be other films on the same topic," he said.