A Nigerian Pentecostal Christian, director of a nongovernmental organization that works for mutual understanding between Nigeria’s Christians and Muslims, alerted me to it. "Have you heard of the Fulani?" he asked at our first meeting, in Paris, speaking the flawless, melodious English of the Nigerian elite. The Fulani are an ethnic group, generally described as shepherds from mostly Muslim Northern Nigeria, forced by climate change to move with their herds toward the more temperate Christian South. They number 14 million to 15 million in a nation of 191 million.
Among them is a violent element. "They are Islamic extremists of a new stripe," the NGO director said, "more or less linked with Boko Haram," the sect that became infamous for the 2014 kidnapping of 276 Christian girls in the state of Borno. "I beg you," he said, "come and see for yourself." Knowing of Boko Haram but nothing of the Fulani, I accept.
The 2019 Global Terrorism Index estimates that Fulani extremists have become deadlier than Boko Haram and accounted for the majority of the country’s 2,040 documented terrorist fatalities in 2018. To learn more about them, I travel to Godogodo, in the center of the country, where I meet a beautiful woman named Jumai Victor, 28. On July 15, she says, Fulani extremists stormed into her village on long-saddle motorcycles, three to a bike, shouting "Allahu Akbar!" They torched houses and killed her four children before her eyes.
When her turn came and they noticed she was pregnant, a discussion ensued. Some didn’t want to see her belly slit, so they compromised by cutting up and amputating her left arm with a machete. She speaks quickly and emotionlessly, staring into space as if she lost her face along with her arm. The village chief, translating for her, chokes up. Tears stream down his cheeks when she finishes her account.
I venture north to Adnan, where Lyndia David, 34, tells her story of survival. On the morning of March 15, rumors reached her village that Fulani raiders were nearby. She was dressing for church as her husband prepared to join a group of men who’d stand watch. He urged her to take refuge at her sister’s home in another village.
Her first night there, sentinels woke her with a whistle. She left the house to find flames spreading around her. Fulani surrounded her. Then she heard a voice: "Come this way, you can get through!" She did, and her putative savior leapt out of the underbrush, cut three fingers off her right hand, carved the nape of her neck with his machete, shot her, doused her body with gasoline, and lit it. She somehow survived. A few weeks later she returned to her village and learned that the raiders had leveled it the same night. Her husband was among the 72 they murdered.
The Christian Middle Belt is a land of blooming prairies that once delighted English colonizers. On the outskirts of Jos, capital of Plateau state, I visit the ruins of a burned-down church. I spot another, intact. A man emerges to yell at me in English that I don’t belong there. Stalling, I learn that he is Turkish, a member of a "religious mutual assistance group" that is opening madrassas for the daughters of Fulani.
That day I crisscross the Middle Belt. Roads are crumbled, bridges collapsed; destroyed houses cast broken shadows over tree stumps and trails of black ash and blood. Maize rots in the abandoned fields. The local Christians have been killed or are too terrorized to come out and harvest it. In the distance are clusters of white smudges—the Fulani herds grazing on the lush grass. When we approach, the armed shepherds wave us off.
The Anglican bishop of Jos, Benjamin Kwashi, has had his livestock stolen three times. During the third raid he was dragged into his room, a gun to his head. He dropped to his knees and prayed at the top of his voice until the thrumming of a helicopter drove his assailants off.
Bishop Kwashi describes the Fulani extremists’ pattern: They usually arrive at night. They are barefoot, so you can’t hear them coming unless they’re on motorcycle. Sometimes a dog sounds the alert, sometimes a sentinel. Then a terrifying stampede, whirling clouds of dust, cries of encouragement from the invaders. Before villagers can take shelter or flee, the invaders are upon them in their houses, swinging machetes, burning, pillaging, raping. They don’t kill everyone. At some point they stop, recite a verse from the Quran, round up the livestock and retreat. They need survivors to spread fear from village to village, to bear witness that the Fulani raiders fear nothing but Allah and are capable of anything.
The heads of 17 Christian communities have come to the outskirts of Abuja, Nigeria’s federal capital, to meet me in a nondescript compound. Some have traveled for days in packed buses or minivans. Each arrives accompanied by a victim or two.
Here they are, an exhausted yet earnestly hopeful group of some 40 women and men, keenly aware of the moment’s gravity. One carries a USB key, another a handwritten account, a third a folder full of photos, captioned and dated. I accept these records, overwhelmed by the weight of the bearers’ hope that the world will recognize the horrors they experienced.
Taking the floor in turn, the survivors confirm the modus operandi Bishop Kwashi described, each adding an awful detail. The mutilated cadavers of women. A mute man commanded to deny his faith, then cut up with a machete until he screams. A girl strangled with the chain of her crucifix.
Westerners here depict the Fulani extremists as an extended, rampant Boko Haram. An American humanitarian says the Fulani recruit volunteers to serve internships in Borno State, where Boko Haram is active. Another says Boko Haram "instructors" have been spotted in Bauchi, another northeastern state, where they are teaching elite Fulani militants to handle more-sophisticated weapons that will replace their machetes. Yet whereas Boko Haram are confined to perhaps 5% of Nigerian territory, the Fulani terrorists operate across the country.
Villagers west of Jos show the weapons they use to defend themselves: bows, slings, daggers, sticks, leather whips, spears. Even these meager arms have to be concealed. When the army comes through after the attacks, soldiers tell the villagers their paltry weapons are illegal and confiscate them.
Several times I note the proximity of a military base that might have been expected to protect civilians. But the soldiers didn’t come; or, if they did, it was only after the battle; or they claimed not to have received the texted SOS calls in time, or not to have had orders to respond, or to have been delayed on an impassable road.
"What do you expect?" our driver asks as we take off in a convoy for his burned-down church. "The army is in league with the Fulani. They go hand in hand." After one attack, "we even found a dog tag and a uniform."
"It’s hardly surprising," says Dalyop Salomon Mwantiri, one of the few lawyers in the region who dare to represent victims. "The general staff of the Nigerian army is a Fulani. The whole bureaucracy is Fulani."
So is President Muhammadu Buhari. In April 2016 Mr. Buhari ordered security forces to "secure all communities under attack by herdsmen." In July 2019 a spokesman for the president said in a statement: "No one has the right to ask anyone or group to depart from any part of the country, whether North, South, East or West."
Most Christians I meet express disgust at the vague language suggesting culpability on both sides. Their stories tend to validate claims of the government’s complicity. In Riyom district, three displaced Nigerians and a soldier were gunned down this June as they attempted to return home. The villagers know the assailants. Police identified them. Everyone knows they took refuge in a nearby village. But there they are under the protection of the ardos, a local emir. No arrests occurred.
Village chief Sunday Abdu recounts another example, a 2017 attack on Nkiedonwhro. This time the military came to warn villagers of a threat. They ordered the women and children to take shelter in a school. But after the civilians complied, a soldier fired a shot in the air. A second shot sounded in the distance, seemingly in response. Minutes later, after the soldiers had departed, the assailants appeared, went directly to the classroom, and fired into the cowering group, killing 27.
I also meet some Fulani—the first time by chance. Traveling by road near a river bed, we come on a checkpoint consisting of a rope stretched across the road, a hut and two armed men. "No passage," says one, wearing a jacket on which are sewn badges in Arabic and Turkish. "This is Fulani land, the holy land of Usman dan Fodio, our king—and you whites can’t come in." The conquests of dan Fodio (1754-1817) led to the establishment of the Sokoto Caliphate over the Fula and Hausa lands.
The second encounter is on the outskirts of Abuja. Driving toward the countryside, we reach a village unlike the others we’ve seen in the Christian zone. There’s a ditch, and behind it a hedge of bushes and pilings. The place seems closed off from the world. From huts emerge a swarm of children and their mothers, the women covered from head to foot.
It’s a village of Fulani nomads who carried out a tiny, localized Fulanization after the Christians cleared out. "What are you doing here?" demands an adolescent boy wearing a T-shirt adorned with a swastika. "Are you taking advantage of the fact that it’s Friday, and we’re in the mosque, to come spy on our women? The Quran forbids that!" When I ask if wearing a swastika isn’t also contrary to the Quran, he looks puzzled, then launches into a feverish tirade. He says he knows he’s wearing "a German insignia," but he believes that "all men are brothers," except for the "bad souls" who "hate Muslims."
Later I encounter Fulani near Lagos, Nigeria’s largest city, which is in the south on the Gulf of Guinea. North of the city is an open-air market where Fulani sell their livestock. I am with three young Christians, survivors of a Middle Belt massacre who live in a camp for displaced persons. They pretend to be cousins buying an animal for a family feast. As they negotiate over a white-horned pygmy goat, I look for Fulani willing to talk.
Most have come from Jigawa state, on the border with Niger, crossing the country south in trucks to bring their stock here. Although I learn little about their trip, they eagerly express their joy in being here, on the border of this contemptible promised land, where they expect to "dip the Quran in the sea."
There are "too many Christians in Lagos," says Abadallah, who looks to be in his 40s. "The Christians are dogs and children of dogs. You say Christians. To us they are traitors. They adopted the religion of the whites. There is no place here for friends of the whites, who are impure." A postcard vendor joins the group and offers me portraits of Osama bin Laden and Turkish President Recep Tayyip Erdogan. He agrees the Christians will eventually leave and Nigeria will be "free."
Some professional disinformers will try to reduce the violence here to one of the "interethnic wars" that inflame Africa. They’ll likely find, here and there, acts of reprisal against the Fula and Hausa. But as my trip concludes, I have the terrible feeling of being carried back to Rwanda in the 1990s, to Darfur and South Sudan in the 2000s.
Will the West let history repeat itself in Nigeria? Will we wait, as usual, until the disaster is done before taking notice? Will we stand by as international Islamic extremism opens a new front across this vast land, where the children of Abraham have coexisted for so long?
Mr. Lévy is author of "The Empire and the Five Kings: America’s Abdication and the Fate of the World" (Henry Holt, 2019). This article was translated from French by Steven B. Kennedy.