Of the hundreds of terrifying incidents recorded by Judy Batalion in her powerful book, The Light of Days, one, perhaps, encapsulates the overwhelming problems faced by young Jews in Poland during wartime.

It was a matter of trust: of how to know whom to trust, or who might betray you in a heartbeat. Batalion writes about an arranged meeting in 1943 Warsaw, after the ghetto uprising in April of that year.

Renia, a young Jewish woman of barely 20, is due to meet Antek, whom she has never met but has heard of from letters and stories in her youth movement. She wears a dress and new shoes, a bright red flower in her hair so that he might recognise her. He will carry a newspaper under his arm, she has been told.

And she sees “a tall, blond young man, with a fine moustache like that of a rich lord”. He doesn’t flicker when she walks by, displaying her flower. And she simply doesn’t know if he is Antek, or if they are being set up, or watched.

Eventually she speaks to him, in Polish. And once he starts talking, she can tell by “his creaky Polish accent” that he is a Jew from Vilna.

That the encounter has a cinematic quality has not been lost on film-maker Steven Spielberg, who has optioned The Light of Days, meaning that Batalion is now engaged, together with screenwriter and playwright Michael Mitnick, in turning her massive book into a screenplay.

Montreal-born Batalion — the granddaughter of Polish Holocaust survivors, who grew up speaking English, French, Hebrew and Yiddish — has been working on The Light of Days for 14 years — “off and on”. Speaking from New York where she lives with her husband and three children, she says that the book went through many twists and turns before settling down to become the largely little-known stories of the women fighters of the Jewish resistance in Poland. Painstakingly pieced together from long-forgotten memoirs and testimonies, and cross-referenced in numberless archives, The Light of Days conjures up a world we barely know about: of Batalion’s heroines, Renia and Zivia, Tosia and Frumka, Bela and Chajke.

The actions of these young women, carefully brought back to life by Batalion, turn much of what we believe we know about the Holocaust on its head. The Holocaust, the book makes clear, did not just happen in the concentration camps, terrible though those were, but also in the ghettoes and the forests all over central Europe. And there was resistance, inspired and angry.

Almost all the young women were products of Zionist or political youth movements. “I was very attracted to them because they were so unlike me”, Batalion says, “they went towards danger, and I am a very nervous person. They were so audacious and unapologetic and determined”. Of all the surviving post-war accounts, “Renia’s really stood out for me. She wasn’t idealistic, her writing wasn’t championing a cause or too caught up in political rhetoric — but she really told a story, even with a little bit of humour or wit”.

A perfect storm of circumstance led to these young women playing the roles they did, often acting as couriers across Nazi-occupied Poland in the most dangerous of situations. First, and sadly most important, was the fact that they were Jewish women and not Jewish men — if caught, there was no tell-tale circumcision to give them away. Many of them were able to “pass” as Aryan and frequently assumed Polish Catholic identities — as Batalion makes clear, wearing “Christian” clothes of the sort never worn by Jews, going to church and taking part in services.

Another crucial factor was language. Many of the women were multi-lingual, switching easily from Yiddish or Hebrew to Polish or German. One, Bela Hazan, needed a job and ended up working in the Grodno Gestapo offices as a translator. According to Batalion, this facility frequently resulted from the tendency among Jewish families to send their sons to yeshivot — and their daughters, whose education “did not matter as much” — to the Polish public schools. So the girls grew up speaking at least two languages, Yiddish at home and Polish outside, with perhaps Hebrew and German thrown in. “This was so important because they learned to speak ‘real’ Polish, not with a creaky Yiddish accent, and that enabled them to disguise themselves when it became necessary”. Educated women spoke Russian and French, too.

Batalion, she says, was “blown away learning about Poland in the 1930s, before the war. My own assumption was that feminism started in the 70s in California, but actually, in Poland between the wars there was mandatory education for boys and girls. Women had the vote in 1918, before many Western countries. Women were allowed to go to university and the majority of those were Jewish women. Many of these memoirs that I read would say something like ‘she shot this Gestapo man and she had a degree in history from Warsaw University’.”

And those who did not go to university worked. “In 1931 almost 45 per cent of the Jewish workforce were women”. This was reflected in women’s fashion, too: “shorter skirts, shoes you could walk in — fashion for function”. Add to that the fact that Jewish women often had leadership roles in the youth movements and you had a cohort of young, able, brave resistance fighters, smuggling guns in loaves of bread or carrying coded messages in braided hair, assuming Christian identities with ease and discarding them as quickly — and even showing breathtaking chutzpah by asking Nazis to carry bags loaded with weapons.

Chasia Bielicka describes this full-on attitude as the women’s “extreme confidence technique”, whereby — even carrying a gun in a box, she was able to accost a Nazi in the street, and ask him: “Do you know what time it is? I’m running late”.

There are three issues in The Light of Days with which Batalion deals with delicacy and tenacity. One is the level of horrific barbaric behaviour by the Nazis in and around the ghettoes. We are sadly familiar with concentration camp atrocities, less so with the Gestapo brutality and torture outside them.

She also does not shy away from the issue of sexual assault against Jewish women, “ranging from humiliation to rape. “Most victims did not know their tormentors’ names”, Batalion writes “Many women were killed after they were raped; others were too ashamed to speak of it, fearing they would no longer be marriage material.

“In concentration and work camps, the Nazis set up official brothels…some Nazis kept personal sex slaves… in one case, pretty Jewish women were chosen to be naked servants at a Nazi’s private feast, after which they were raped by the guests…

“Chasia Bielicka related that at a camp near Grodno, Jewish girls and women whom the commandant deemed beautiful were given evening gowns and delivered to German parties. Each woman, in turn, was asked to dance with one of the men in front of all the guests”. And then the commandant would produce a handgun and shoot the woman in the head.

And the third issue is what happened after the war, when those who survived had made it to the new state of Israel. And that doesn’t make for pleasant reading, either. Those women who had poured their hearts and souls into resistance were often not believed, or, having undergone torture or sexual abuse, were ashamed to talk about their wartime experiences. There was a hierarchy of suffering, it emerged, from those who had survived the concentration or slave labour camps, to those who had “merely” been passionate defenders of the Jewish people and activists in the resistance network.

Zivia Lubetkin, a heroine of the Warsaw Ghetto Uprising in 1943, was taken up by the early Labour Zionists, but her story, says Batalion, was “edited to toe the party line”. It is not an edifying conclusion.

“For me,”says Batalion, “as important a question as ‘what is this story?’ is ‘why don’t I know this story?’ And there are many reasons, some having to do with the zeitgeist, social, intellectual, but a lot of it is personal. Sometimes they did tell their stories and they were greeted with ‘the pure souls perished, and what did you do to survive? They were accused of sleeping their way to safety, of abandoning their families… and many of the women also felt a very profound survivor guilt”.

As Batalion points out, her protagonists were aged between 17 and 22 during the war. Renia, her main character, was just 20 at the time she arrived in mandate Palestine. “She had the rest of her life in front of her. They had to start over from nothing. For many of them, they had to put the story away and they wanted their lives to be normal.”

One thing for Batalion is very clear: “I was making history out of memoirs”. These are the women whose voices have not been heard for decades. This book brings them back on to the stage, where they belong.

The Light of Days by Judy Batalion is published by Virago