Having addressed the wartime occupation of Poland in films such as Ashes and Diamonds (1958), and its later experience of communism and dissident trade-unionism in Man of Marble (1976) and Man of Iron (1980), the 82-year-old director Andrzej Wajda has now tackled the most painful, most personal subject of all the Katyn forest massacre of 1940, a subject of enduring rage and shame.

On Stalin's orders, the Soviets slaughtered some 22,000 Polish prisoners of war in Katyn forest near Smolensk in western Russia - mainly military officers and professional-class civilians. The postwar Polish government had to kow-tow to the Soviet Union by backing its claim that the Nazis had been responsible, a claim that Britain's Foreign Office did not dispute and which was only finally contradicted by Mikhail Gorbachev in 1990. The victims of the Katyn massacre included the director's father, Captain Jacub Wajda.

Wajda's film is a powerful and even remarkable memorial to these victims and to the belated destruction of one of the most persistent untruths about the Second World War. His film is not merely about the crime itself, but the process of collusion in which the postwar Polish In 1940, the Soviets slaughtered some 22,000 Polish prisoners of war in Katyn

state sought survival by swallowing what most knew to be a lie about the mass murder at Katyn. For years, in this country and elsewhere, disputing the official line was considered to be the exclusive, seedy preserve of the extreme revisionist right. But Wajda is a film-maker with the artistic and moral authority to say what was long unsayable. The scenes in his movie that show the Nazis, having smashed and bullied the Polish people, self-righteously cranking up their propaganda machine about the Soviets at Katyn have an irony and horror that is impossible to stomach.

Katyn begins with the dual invasion of Poland in 1939, sandwiched by the twin tyrant cynics of the Molotov-Ribbentrop pact from the west, the Nazis, and from the east, the Soviets, who take prisoner virtually the entire Polish officer class. Anna, played by Maja Ostaszewska, is desperately looking for her husband Andrzej, played by Artur Zmijewski, a Krakow cavalry officer who has been captured - and whose father, a university professor, is sent away by the Nazis to be murdered in Sachsenhausen concentration camp. Jan Englert plays the wife of a slaughtered Polish general; she declines to cooperate with the Nazi propaganda effort after the Germans discover the forest grave in 1943. Andrzej Chyra is Jerzy, a Polish army lieutenant and survivor of the war, who knows the awful truth about Anna's husband and cannot bear the burden of guilt at the knowledge he has helped to suppress. Finally, there is Agnieszka, played by Magdalena Cielecka, whose brother was killed at Katyn she is obsessed with the only way to bear witness to the truth. She wants to erect a marble headstone to her brother, simply bearing the true date of his death as 1940, the date at which only the Soviets could have carried out the killings.

Wajda's story begins with the confusion and agony of war's outbreak, then moves on to the confusion and agony of occupation and then the confusion and agony of the postwar settlement. It is a story of embattled civilian life, of people not knowing what is going on or what to think, and realising that the majority of what they are being told by the authorities is untrue. The actual, moment-by-moment horror of the Katyn slaughter itself is saved for the final sequence. It is a narrative ordering that is intended to mimic the way in which the crime was buried in the collective memory and only disinterred long afterwards.

This is a film made with great moral seriousness, and with a clear-eyed deliberation it is sombre and measured as it treads carefully around this most contentious mass grave in Polish history. Yet there are flashes of poetry and tragedy. When Anna is desperately looking for her husband in the chaos and confusion ushered in by the Nazi invasion, she arrives at a churchyard, at which we have time to register a bizarre and painful touch a statue of the crucified Christ has evidently been knocked down - only a nailed hand is visible on the cross. Moments later, Anna sees a body under a blanket, and fears it might be her husband's corpse. But wrenching away the blanket, she finds that it is ... the figure of Jesus. From some scruple of Catholic decency, someone has draped this icon like an injured combatant Jesus has been transformed into a casualty of war. It is a brilliant yet low-key surreal moment, and a hint of what is to come crushed innocence and cover-ups.

Since it was premiered at the Berlin film festival in 2007 - which is where I first saw it - many have wondered if Wajda's Katyn would ever arrive in the UK. There were industry murmurings that audiences here would have no appetite for it. I can't agree; this powerful, heartfelt and important drama from one of the great names in world cinema deserves to be seen in Britain.—Dawn/The Guardian News Service