The gruff phrase “Komm Frau!” – Come, woman! – still sends shivers down the spines of elderly Germans. It was the command given by Russian soldiers as they prowled Berlin and other bombed-out postwar German cities, searching for women to rape.

The hidden horror of those months is about to be revealed in a new German film, A Woman in Berlin, that is likely to shock the nation, stir resentment against the Russians and provoke a debate about morality in war.

The film is based on a diary written by the German journalist Marta Hillers. She began to scribble it in a dusty cellar on Friday April 20, 1945 – Hitler’s birthday, the last before his suicide ten days later.

Within days of the occupation she had been raped several times by Red Army soldiers, one of many hundreds of thousands of German women abused in this way. It was the crime that no one talked about.

In communist East Germany, where the Soviet Union was hailed as friend and protector, the dark days of postwar rape and abuse were forgotten; in West Germany they were locked away among family secrets.

“The German soldiers came back from the war and did not want to know about the humiliation of their wives, daughters, even mothers,” says Nina Hoss, who plays the lead role in the film that opens in Berlin this week. “There was a double silence: the men about what they did on the front; the women about their suffering.”

Hillers, who died in 2001 aged 90, wrote the book anonymously, afraid of the reaction to her confessions. It was published in Britain and the US in the 1950s but was shunned by Germans when it appeared there.

Since then the question of the rapes has been tackled by historians but Germans have tried to avoid the subject: it upsets too many memories about their grandmothers. A reissue in 2003 in Germany was more widely read but often seen as a novel rather than an historical document.

“I only understood later why my mother had an aversion to the Russian language, garlic and vodka,” says Renate Meinhof, a sociologist. “Only after German unification in 1990, when I began to study postwar rape, did I grasp she, too, had been a victim.

“I spoke with women who had been raped by Red Army soldiers and found that because they had stayed in socialist Germany, they had kept their emotional wounds bandaged up for decades.”

The film lays it all bare. By the time the soldiers arrived they had vented most of their fury, their hunger to revenge themselves for atrocities committed by the Germans in the east. Instead they enter the cellars to shine their torches on cowering women until they find a victim.

The author of the diaries described how they particularly favoured fat women, chasing the local baker’s wife through the rubble until they managed to pin her to the ground. The film stops short of showing some of the most grisly scenes from the diary and tries to avoid depicting the Germans as simple victims – a charge that has been levelled against other recent films depicting the Third Reich, including The Downfall.

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