As a junior researcher on a TV documentary in Uganda in 1986, I was told to ask a question that was the dark cliche of war reporting: “Anyone here been raped and speak English?” To my horror, a teenage girl stepped shyly forward, eyes cast downwards. Since then, I have come across hundreds of women raped in wars around the world – and I have found kinder ways of establishing if they want to tell their story.

In her harrowing new book, foreign correspondent Christina Lamb explains that rape in conflict is often seen as a “private crime”, an incidental atrocity, when it is “as much of a weapon of war as the machete, club or Kalashnikov”. She gives priority to the stories of individual women, many of whom feel validated by speaking out, but understands why other victims remain silent. Often they feel ashamed, or fear ostracism from their own communities. “You won’t find these women’s names in the history books or on the war memorials,” Lamb writes. “But to me they are the real heroes.”

Despite being a common battlefield tactic, rape has been largely ignored in historical accounts, featuring in neither the second world war history textbooks Lamb read in school, nor those her son studied. It took half a century for the Japanese government to acknowledge the harm done to the “comfort women”, an agonising euphemism given to Koreans and others forced into sexual slavery by the imperial Japanese army. Although reports existed, the mass rape of German women by Stalin’s forces as they entered Berlin in 1945 was not widely known until Antony Beevor wrote about it in 2002. The Russian government still denies it happened.

Despite being a common battlefield tactic, rape has been largely ignored in historical accounts, omitted from history textbooks

More recently, journalists and medical staff have reported mass rape in Bosnia, Rwanda and the Democratic Republic of the Congo, where even babies have been sexually abused, earning the country the sobriquet “the rape capital of the world”. But, distressingly, greater awareness through the 1990s and 2000s has not acted as a deterrent. During their three year rampage through northern Iraq and Syria starting in 2014, the Islamic State leadership declared that fighters could sexually enslave Yazidi women because they were not Muslims. In Myanmar in 2017, Buddhist government forces carried out mass rape against the Muslim Rohingya.

Inevitably, Lamb has sombre thoughts. “What enjoyment could men get from abusing women in such a way? ... Are men somehow hardwired to hurt women?” War is a time when rules are broken – if killing is legitimised then it’s not entirely surprising that other norms are also breached. But rape is often integral to how a war is prosecuted. Commanders may tolerate or even order rape to humiliate the enemy, traumatise the population so they flee, and impregnate women to change the demographic balance of a country or region. In Syrian prisons, men are also raped as a form of torture.

Lamb’s attempts to interview perpetrators don’t get very far. The Isis prisoners she meets deny that they raped – it’s always someone else who kept a Yazidi slave, although, suspiciously, they seem to know a lot about the practice. Lamb asks why some armies rape and some do not. The British raped less than other armies during the second world war, mainly due to their military culture. Despite the brutality of the conflict, there are few reports of Israeli soldiers raping Palestinians, possibly because one-third of the soldiers in the Israeli Defence Forces are women, a far higher proportion than in most armies.

Slowly, attitudes to rape in conflict are changing. In 2018 the Nobel peace prize was awarded to the Yazidi campaigner Nadia Murad – herself a victim of battlefield rape – and Dr Denis Mukwege, a surgeon from the DRC. At Panzi hospital in Bukavu, Mukwege has pioneered a holistic approach that starts with surgical procedures to repair physical damage done to women, and proceeds to psychotherapy, financial support and legal advice. Mukwege is clear that in the DRC, soldiers rape as much as irregular bandit forces. As a result, his life is in constant danger. “It takes time, but the only way we can change society is to end impunity,” he tells Lamb.

Some glimmers of hope lie in the changing legal environment. Navanethem Pillay, a judge at the international criminal tribunal for Rwanda, realised that the detailed testimony of rape provided by female witnesses was central not peripheral to charges of genocide. Lamb’s interviews with the pioneering Rwandan women who overcame fear and stigma to testify are especially moving. Eventually prosecutors added rape and sexual violence to their indictments. It was the first time that rape was recognised in an international court and prosecuted as part of genocide. The international criminal tribunal for the former Yugoslavia went further, ruling that systematic rape and enslavement could be treated as torture and thus a war crime. Again it was a female judge, Florence Mumba of Zambia, who presided over the initial conviction.

In the #MeToo era, the impetus is to believe women – Lamb quite rightly does, while never losing her journalistic rigour

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Given these legal advances, it’s disturbing to note that no one has yet tried Isis members for the rape of Yazidi women. At the international court of justice in The Hague last December, the former political prisoner and darling of the human rights community, Aung San Suu Kyi, now State Consellor and effectively prime minister of Myanmar, said her country’s military courts could handle any alleged atrocities by soldiers against the Rohingya. She made no mention of rape. Nor has there been any effective action against members of the Nigeria-based jihadi group Boko Haram, who continue to kidnap and enslave women. The fate of the 219 schoolgirls kidnapped from the village of Chibok in 2014 reveals the limits of international pressure. Despite hashtags and outrage from celebrities, including Michelle Obama, then US first lady, the Nigerian government failed to mount a rescue when it might have been possible. Negotiations resulted in the liberation of some girls, but most are missing to this day.

At times, Lamb worries that she is being intrusive, but she is also careful not to be credulous. An experienced journalist, she can tell when something doesn’t smell right – one Rohingya woman in a camp in Bangladesh has a long story that doesn’t add up. In the age of #MeToo, the impetus is to believe women and on the whole, she – quite rightly – does, while never losing her journalistic rigour. The litany of pain she recounts is all too believeable. I know because I have heard it too.

“This has been in many ways a journey through the worst depravities of man and I thank you for bearing with me, for I know it has not been an easy read,” she writes. But silence is the women’s worst enemy, and that’s why, while some may be tempted to turn away from the horror, this is such an important book.

• Lindsey Hilsum’s In Extremis: The Life of War Correspondent Marie Colvin is published by Chatto. Our Bodies, Their Battlefield by Christina Lamb is published by William Collins (RRP £20). To order a copy go to guardianbookshop.com. Free UK p&p on all online orders over £15.