A nearly full moon was the only light over the village of Kavumu, in eastern Congo, on the night of 26 December 2015. Just before midnight, a figure slipped quietly through the shadows along the red-earth tracts between huts and entered one of the wooden shacks. The intruder proceeded to take a three-year-old girl called Denise from the bed where she was sleeping next to her mother. Also at home that night were two women and three other children. None of them heard anything.

Denise’s mother woke up after midnight and groped for her daughter next to her on the mattress. She found only an empty space. An iron bar normally used to block the door was on the floor. A machete was stabbed into the ground outside the entrance. The women recognised the signs: this scenario had been repeated in Kavumu many times in the previous two and a half years.

The family woke the neighbours, who spanned out into search parties. In a nearby field, beneath stalks of sorghum, corn, and desiccated cassava, they soon found Denise lying on the wet dirt, wearing only her fuchsia-pink hoodie. She had been raped and was badly hurt, bleeding from between her legs. They took her straight to the local hospital and one of the search party was sent to notify the village chief and police of the attack. Denise spent the night in hospital and the next morning, she was sent to Panzi hospital, a much larger facility in the provincial capital of Bukavu. In the early days of the attacks, untrained medical staff in Kavumu had been washing away evidence in an attempt to clean up the girls, but Panzi doctors had since instructed them on how to treat victims of rape in a way that preserved forensic evidence.

Denise was, by some counts, the 39th child to be raped in the village of Kavumu, since the first was reported on 3 June 2013. Each time, men in groups had kidnapped a girl of between 18 months and 11 years old from her bed, raped her, and either returned her to her home or left her in a nearby field, which is farmed by demobilised soldiers. At least two girls have died from their injuries.

Although rape has been used as a weapon of war in this part of the Democratic Republic of the Congo (DRC) for 20 years, these attacks on children are new – in terms of the repeated patterns, the symbolism and the youth of the victims. At first, the cases didn’t appear to be related. But over time, as each abduction resembled the last in certain significant details – the way men entered the houses; the way the girls were taken, violated and returned or left in the same field; and the fact that none of the families woke up as men stole their children – investigators began to suspect that there was an organised ring behind the attacks.

Because the girls are so little, their organs are often irreparably damaged. Panzi hospital’s founder and medical director, Dr Denis Mukwege, said that he and his staff frequently weep while operating on the girls. Another doctor said the brutality of the rapes made her faint for the first time in her life. “When I treat a child with all her bladder and abdomen destroyed, I think, This is really not something I want to do with my life,” Mukwege told me. We were sitting at a long, plastic-covered table in a conference room at Panzi in January. He looked exhausted. “You are thinking about how you are just repairing and instead you should be preventing this.”

And yet, despite the horror of these attacks, the news has barely trickled out of DRC.

“Everyone should be shocked by this,” said Mukwege. “But why aren’t they?”

Earlier in the week that Denise was taken, two other girls, aged five and six, were also gang-raped in Kavumu. All three now lay in beds shrouded in mosquito nets in Panzi hospital’s cavernous sexualised violence ward, medicated with antibiotics, antiseptic and painkillers. One child, the six-year-old, was particularly small and appeared catatonic – she sat unresponsive in her bed with her green-flowered shift dress falling off her shoulders. The girls spoke to me with their mothers. The children’s voices went whispery and the life seemed to leave their eyes when they talked about the attacks. All looked at their hands or the ground as they spoke.

The girls will reach puberty before they and their families know the extent of the physical and psychological harm done to them. “We don’t know if they will have sex normally because of fibrosis,” the girls’ doctor, Dr Neema Rukunghu (known to all as Dr Nene), said, “Because of destruction of the cervix, we don’t know if they will bleed normally or have babies. We don’t know.”

For the Kavumu families caring for their “ruined” (as they put it) daughters, every day that passed brought new terrors. “We don’t know who will be the next child visited by the rapist,” one mother said. (The families asked that I not use their names in order to protect them from retribution.) They had gathered in a sweaty, dim room and crammed on to benches, chairs and the floor in order to tell their stories and talk about their fear.

“Now,” the mother said, “we no longer sleep.”

Facebook Twitter Pinterest Kavumu is described as a ‘very, very poor’ village by people who live in one of the poorest countries on Earth. Photograph: Lauren Wolfe/The Guardian

Kavumu is described as a “very, very poor” village by people who live in one of the poorest countries on Earth. It is in the province of South Kivu, where fighting between different groups has dragged on in bursts for years. Next door is the 1.5 million-acre Kahuzi-Biega national park, a Unesco world heritage site of tropical forest that is home to eastern lowland gorillas – and, since 1996, a number of armed groups fighting for control of land, natural resources and political power, fuelled by ethnic tensions and outside interference. Over time, some of these rebels have moved from the park over to Kavumu, bringing with them the threat of violence. “It’s a strange environment,” said one international NGO researcher who asked not to be named for fear of reprisals. “People are thrown together that shouldn’t be.”

Families in Kavumu generally make a dollar or two a day selling small quantities of fruit, charcoal or cassava. When I visited in December and January, children in torn shirts playfully ducked out from behind outhouses that were built from a patchwork of dirty, torn tarps. A pig foraged near some shacks, and roosters and goats made discontented noises.

The village was in deep trauma. Many people were troubled by night terrors. One father had spent every night keeping guard by the door since his daughter was abducted, in case the attackers came back; he could no longer work because he had to sleep during the day. Locks, where they existed at all, were generally a couple of bent nails with a bar slipped through them. They could easily be levered open from the outside. Some doorways were only covered with a curtain.

Those who have been abducted have been alienated from the community, because of the stigma of girls who have been raped

The fear that the attackers may return to the same house was well founded. An 11-year-old girl named Yvette had been kidnapped and raped on two separate occasions, once at the end of March, the second time in August. She picked at a mosquito bite on her arm while she told me her story. Not only had she been assaulted twice, but the other children at school abused her for it, “because I was destroyed and they were not”, she said. Kids had singled out Yvette as the girl who had been taken, a psychologist at Panzi, Justin Cikuru, said. “Children feel uncomfortable and so they tease her.”

Those who have been abducted in Kavumu have been alienated from the wider community, because of the stigma of girls who have been raped. At first, each assault was treated in isolation, because the alternative was too terrible to contemplate – that there was some kind of organised campaign targeting the village. A division grew between the families whose children had been attacked and the rest, who did not want to be involved. “It’s a community in denial,” said Cikuru.

The victims and their families tended to keep to themselves. One reason for their silence was fear of retribution from both the perpetrators and the authorities. For 20 years, sexual violence has been inflicted by militias and the Congolese army. Perpetrators have visibly scarred rape victims to ensure they carry the stigma. For years, president Joseph Kabila denied that rape was a problem in the country, but in 2009, he seemed to change his mind, and declared a “zero tolerance” policy. In the past couple of years, official UN and DRC government records of the number of women assaulted in the eastern part of the country have ranged from 12,000 (over nine months in 2014) to more than 15,000 in 2015. And these numbers, according to experts, are probably just a fraction of the actual counts.

Government assistance for victims has been basically nonexistent. Reparations for victims of rape have been ordered by the courts, but not a single survivor has ever been paid. (The only payout was made to the wrong people: in 2014, a lawyer fraudulently claimed compensation for 29 women who posed as rape victims.)

In 2015, Kabila appointed a special representative on sexual violence, Jeanine Mabunda. She had previously held governmental and corporate positions, including minister of state-run companies. She is also on the board of Randgold Resources, a mining corporation which has its headquarters in Jersey. Her office has hired PR firms Crescent Consultants and KRL International in Washington, DC, at great expense, to represent her in the media and sell DRC to investors. That large sums have been spent curating her office’s public image does not sit well with Kavumu’s task force, since investigations into the attacks were stalled for more than a year by lack of funding. The same problem of funding has disrupted basic services throughout the country. Officials and members of the army and police are rarely paid, so they often try to gain money in other ways – a phenomenon I experienced in December, when I was detained by the Congolese intelligence services for several hours. One of the men in charge of my interrogation admitted he had not been paid for three months. One staffer repeatedly suggested I “help him out”, but I was eventually released without handing over any money.

In such an atmosphere of corruption and distrust of the authorities, as Dr Cikuru said: “You fear the consequences if you say the government is not protecting your community. So you stay quiet.”

One local police officer has made it his mission to solve these crimes. He, too, cannot be named for fear of reprisals but he was the man who drove three-year-old Denise from Kavumu to the hospital in Bukavu the morning after she was attacked. He cried as he picked up the little girl in his arms, carried her to his own car, and drove an hour and a half, over potholed roads, to Panzi. After months of struggling to stop the attacks, thwarted by a lack of government funds and trained investigators, he was worn out.

You can’t imagine what it’s like, every time they call me to say that yet another child has been raped A local police officer

“I felt like I was powerless,” the officer said when we met in the provincial capital Bukavu in the early evening, two days after the attack on Denise. “She was too small.” He sat forward on the edge of his chair. “I’ve experienced cases in which a parent kills a child because they want money; rapes of women that entail using sticks inside them; rapes like in Walikale, where 300 were attacked; many cases. But this is the biggest investigation of my career.” The stress weighed on him. His shoulders hunched. “You can’t imagine what it’s like, every time they call me to say that yet another child has been raped.”

By September 2014, the attacks had become regular occurrences in Kavumu, but still the government refused to consider the possibility that the crimes were linked. After the first spate of child rapes, the Boston-based NGO Physicians for Human Rights, which documents human rights abuses and advocates on behalf of persecuted health workers, started pushing for the attacks to be treated as a mass crime. Dr Ellinor Ädelroth, a Swedish specialist in public health, became project manager for Panzi hospital’s sexual violence programme in December 2014. In her first weeks in the job, she compiled a dossier on nine Kavumu child rape cases and presented them to a few Swedish United Nations Police (Unpol) investigators she knew in Bukavu. (The UN Stabilisation Mission in Congo (Monusco) is the world’s largest military peacekeeping force. Its police wing, Unpol, is tasked with building up the national police force through training and development of law enforcement.)

Facebook Twitter Pinterest A plantation near Kavumu. Photograph: Lauren Wolfe/The Guardian

The information was passed on to different groups working on the protection of women and children. A non-governmental Kavumu task force had been formed in May 2014, based in Bukavu, consisting of Monusco, other UN offices, Physicians for Human Rights and doctors from Panzi hospital. But not all parties in the group were agreed on strategy. Some members of the task force, which was meant to co-ordinate responses to the attacks and collect information, wanted to hold a press conference in Bukavu to tell the international press what was happening to girls in Kavumu but, according to Ädelroth, Monusco opposed the idea. Another source, who asked to remain anonymous, said the idea was quashed “due to the political sensitivity it could raise about Congolese authorities, mainly due to their poor response in terms of prevention and the [lack of] evolution on the justice and prosecution procedures”.

Through 2015, no arrests of any consequence were made. Girls continued to arrive at Panzi hospital on a regular basis, having been violently raped. One UN official resigned out of frustration at the UN’s continued failure to halt the atrocities. Each of the different UN sub-departments in DRC has its independent function; the Kavumu task force had come into being in response to the crisis, but coordinating efforts was no simple matter.

When Physicians for Human Rights set about stringing together a pattern of violence, with the help of the local police officer and the doctors at Panzi, the United Nations Development Programme (UNDP) and others stepped up with financial and logistical support, donating not just funds but things such as office furniture and cars. Yet even with this support, local investigators were so under-resourced that, on one occasion when I was in Bukavu, they had to call around to different NGOs trying to find $250 to pay for fuel and photocopies to file legal papers at the tribunal in Kavumu.

“We need the culprits arrested,” Irma van Dueren, Monusco’s senior women’s protection adviser, told me in February. “We are frustrated about how long it’s been taking. Be assured though that this is at the top of the agenda.”

Some of the parents of victims, frustrated and bewildered by the government’s inaction, became convinced that the attacks were part of a conspiracy. “We think that the politics of destroying children is something decided on by the leaders of the country,” one mother said. “Because we see government people coming to investigate and you expect a certain kind of help from the government. But nothing happens.” She wondered if the attacks were a scheme to make money from the families. A number of parents reported that when they went to the police the night their daughters were raped, they were arrested and had to pay a bribe of up to $100 to be released. In one case, the injured daughter had been taken into custody, too.

Three men had been caught by family members as they tried to steal girls away or, in one case, as the assault was taking place. In February 2013, a girl named Isabelle, aged 10, was discovered missing by her mother, who then sent her older brother to look for her. While searching, the brother heard noises coming from one of the shacks. He looked through the gaps of the wooden slats of an outer wall to see his sister being raped. Soldiers were called and they caught the man with his pants around his ankles. As had happened to other families, they also arrested Isabelle’s father, but released him without charge. The perpetrator, according to Isabelle’s father, bought his way out of jail for $400. Isabelle shrunk into her heavy polyester dress as she told me, “God will punish them one day.”

Three or four other men have been arrested – according to newsletters from Jeanine Mabunda’s office – although sources told me that some of them may have had nothing to do with the attacks. The men have reportedly been sentenced to between 10 and 12 years, although it is not clear where they are serving their time or whether they are even still in jail.

It wasn’t until March 2015 – nearly two years after the rapes began – that Mabunda was dispatched to the country’s eastern border to meet with the Kavumu task force. A month later, her office put out a statement saying the government “will launch an investigation” into the attacks, but no one came to talk to the girls, or their families.

In May 2015, the UN refugee agency’s Bukavu office posted billboards in four areas of Kavumu decrying child rape; one showed a girl tied to a tree while two men buckled up their pants, accompanied by the slogan: “Break the silence, denounce sexual violence”. The UN Refugee Agency, which has a presence in this area to manage the many thousands of people displaced by conflict, had decided to undertake a programme of what it calls “sensitisation” to teach people to not tolerate the rape of children in their community.

But breaking the silence is not a simple matter. One well-known human rights campaigner named Evariste Kasali, a coordinator for NGO Organisation Populaire pour la Paix, was investigating allegations of abductions and child rape in Kavumu, and spoke out about the authorities’ apparent inability to stop them. On 17 March 2016, he was shot dead at his home in Kavumu.

By mid-2015, local police had started looking for patterns. One detail that resurfaced regularly was that the families of the girls abducted remained asleep while the break-ins occurred. The mother of the two girls who were taken the same night was convinced, like many of the parents, that there were supernatural forces at work. “Imagine you are sleeping and they take someone from you without your knowing,” she said. “Can’t you say that this is witchcraft?”

Many medicinal plants grow in the region’s remarkably fertile soil, and while locals worried about witchcraft, investigators looked for a combination of herbs or roots that would put a person into a deep sleep.

In one case, the police arrived at a house in which the parents were still sleeping after the abduction and rape of their child. Police carried the parents outside, still unconscious. They didn’t wake up until they were at the police station some time later. The rape victims didn’t initially seem to feel pain, which made investigators think some kind of anaesthetic might have been used. They started looking for anyone expert at mixing plants into potions.

In addition to multiple organised foreign militias inside DRC’s borders, there are also many local militia groups formed by people dissatisfied with the government, or who simply want to assert their own power. These groups are known as Mai-Mai, which literally means “water water” – either because the men douse themselves in “magic” water to protect themselves from bullets, or because bullets are said to harmlessly pass through these men like water instead of flesh. Over the years, Mai-Mai militias have kidnapped large numbers of women in both South and North Kivu, taking them into the bush to provide sexual services, according to Human Rights Watch.

Near Kavumu is a town called Lwiro, the main feature of which is a defunct university for the study of natural sciences built in a pink, Spanish-colonial style, which now houses a chimpanzee reserve. If you walk for 20 minutes along a sunken muddy rivulet past the campus, you come to a heavy stone church in a green pasture overgrown with sunflowers. Investigators began looking into a militia based in the town. In July 2012, a German botanist named Walter Müller had been murdered in Lwiro, just beyond the church, close to the perimeter of a huge plantation he owned.

Facebook Twitter Pinterest The church where Walter Müller was attacked. Photograph: Lauren Wolfe/The Guardian

Müller had come to DRC in 1965 to work for a German pharmaceutical company named Pharmakina. When Müller, a short man with black hair and a limp, took over the plantation in the late 1960s, he fired many of the hundreds of people who had worked the land for years. While Müller spoke Swahili and Mashi and was considered by many to blend into local society, his decision to sack so many of the men created bitter resentment that turned to violence. Müller had to get warrants to force the workers out.

Decades later, displaced and disgruntled workers, along with disenfranchised former soldiers and rebels, found a leader, Frederic Batumike Rugimbanya, a member of parliament for South Kivu, who appears to have organised them into a private army that forced Müller off his own plantation.

Resentment towards Müller, who still felt he had a legitimate claim to the land, culminated on a hot, humid day in 2012 at the church. Armed men found Müller there and dragged him to the plantation, where they beat him, stabbed him with spears and left him gravely wounded. When government soldiers found him, Müller was taken to a hospital in Kigali, Rwanda, where he died six days later.

Batumike is 62 years old and the father of nine children. He is known as “10 Litres” because of his small stature (10 litres is the size of a jerrycan commonly used to carry water). Since 2006, he has been elected twice to South Kivu’s parliament. He belongs to the CCU party, which is part of an alliance with President Kabila’s PPRD party. He has long been known around Kavumu as a defender of human rights, although no one could tell me why. He is also a local spiritual leader who conducts Saturday services at a church in his own home.

His grand house has smooth whitewashed walls and a sturdy red roof, which distinguish it from what are otherwise mainly wood shacks. He preaches a Christian service, but with what locals call an African orientation – he believes in the power of nature and spirits. More than one person described how, in his capacity as a pastor, Batumike buried locals wrapped in plastic – not a common practice in DRC.

Batumike and his men convened every week at the plantation, according to locals. They had weapons and frequently used them in skirmishes with the Congolese army, defending their illegal claim to Müller’s land, which the men profited from greatly, according to officials, renting out plots and selling whatever was grown. (Müller was well known for cultivating a wide variety of plants and herbs on the plantation, including Cinchona, or Fever Trees, used in the production of quinine, although what grows there now is a mystery; it’s too dangerous to enter.)

As police and local groups started pooling their information, it emerged that attacks by a local makeshift militia on Congolese army positions increased every time a child was raped. This fuelled suspicion that the attacks were inspired by sorcery: among some rebel groups in DRC, virgin blood is believed to fortify them and make them impervious to bullets. Investigators could not afford to ignore the rumours. “The people who are doing this believe in it,” said one official.

Facebook Twitter Pinterest Batumike’s grand house with its smooth whitewashed walls and a sturdy red roof. Photograph: Lauren Wolfe/The Guardian

By the time I left South Kivu in January, local police had their suspects, but seemed powerless to act. Months passed, and the authorities made no move to issue arrest warrants and end the nightmare in Kavumu. By 20 June, four more girls had been abducted and gang-raped.

At this point, I wrote an opinion piece in the Guardian, accusing the government of allowing the perpetrators to commit these terrible crimes with impunity. The following day, I awoke at 3am in New York to a message from Kavumu saying that the police had a suspect in custody. One hundred and twenty Congolese army soldiers had apprehended the alleged mastermind, Frederic Batumike, and 74 of his men, in an early morning raid. (A number of those arrested were quickly released.)

Batumike was charged with the Kavumu gang rapes, along with 67 men, who were suspected of forming part of his private militia. The men have also been charged with crimes against humanity, participation in an insurrection, and the assassination of military personnel. They are also chief suspects in the murders of human rights campaigner Evariste Kasali and the plantation owner Walter Müller.

“The militia that works for [Batumike] recruited a fetishist who advises the militiamen to rape very young girls to be assured of having a supernatural protection,” justice minister Alexis Thambwe said in an announcement. One official confirmed that this fetishist, who makes the “magic powder”, is also now under arrest.

The case has been classified as a crime against humanity because the attacks have been systematic and widespread, and perpetrated against a civilian population. This classification lifts any kind of time limit otherwise imposed by Congolese law to investigate and try the cases.

Partly thanks to heavy lobbying by the Kavumu task force, the government has shifted the cases’ jurisdiction from the civilian system to the military courts – considered marginally more effective at bringing cases to trial. Even so, the military judicial system is still unreliable: in November 2012, soldiers rampaged through the town of Minova in South Kivu and raped at least 76 women. There was an international outcry when out of 39 defendants, including officers, only two low-level army men were convicted.

The protracted series of kidnappings and rapes has taken a terrible toll on the girls of Kavumu.

Back in Panzi hospital’s low-lit conference room, as rain muddied the world outside, Dr Mukwege slowly shook his head. “With other women, I can keep going because I can see when you help them in the correct way how they can change their own life and the life of their community. They are strong enough to fight for their rights, but with children it’s a trouble for me. I can’t answer why or what will be the future – what will happen to them after they go through these terrible things.”

“It’s good that arrests have been made,” said the father of one of the victims. “We hope that justice will be done, but to tell the truth, none of us has much confidence in Congolese justice. If the suspects are not brought to trial quickly, things will be worse than before. If some of the men are still at large, they are liable to take their revenge. The authorities have shown themselves unable or unwilling to put a stop to this horror, and I no longer feel that DRC is my country. This is not my home. We are all traumatised. We’ve reached our limit: we’re ready to fight back now and we won’t be held accountable for our actions.”

His daughter, sitting quietly, whispered that she didn’t have a lot to say. “Since those men in uniform ruined me, I have not been well. But I don’t even know what’s wrong with me. I’ve asked papa to build a big fence so they can’t come back and hurt us any more.”

I went to visit Yvette, the girl who’d been abducted and raped on two separate occasions. Her house was being rebuilt after her attack to make it more secure, but the work had stalled because the money had run out; there were branches for walls and only half a tin roof in place. Earlier in the day I had given her a notebook to scribble in while I interviewed others. She returned it to me with a story she had written in Swahili, begging for the “people with good hearts” to help her find a safe home: “I fear if I go back home to my own house I will die,” she wrote.

Officials are now saying there may be up to 700 men involved in Batumike’s militia, which means that only a fraction of the group is currently in custody. It is not at all clear that peace has come to Kavumu.

One evening at the end of my stay in South Kivu, as the waters of Lake Kivu gently rippled below, the local police officer talked with equanimity about the danger of retribution. “People like us need accept the risks that will put an end to these kind of crimes. If we don’t risk our lives, then this will go on for ever. But if these guys kill me, they won’t go unpunished,” he said. “People will know who they are – that they killed me because I was investigating their cases. There will be justice.”

The victims’ names have been changed.

• Follow the Long Read on Twitter at @gdnlongread, or sign up to the long read weekly email here.