The call came in to Gary Roberts last March at his home in Béré, a village of subsistence farmers deep in the sorghum and cotton fields of southern Chad. Reports were circulating, a local conservationist told him, that a mass killing of elephants had occurred some 100 miles away, near the Cameroon border: Could Roberts see what he could find out?

Roberts, 36, a Seventh-day Adventist missionary, experienced bush pilot and amateur conservationist who sometimes flies research missions for Chad’s wildlife department, climbed into his single-engine, four-seat Cessna. He took off from the mission’s dirt airstrip and headed north toward the border. Roberts cruised for three hours over a vast green carpet—low-lying brush, sorghum fields and stands of acacias, broken by an occasional dirt road or cattle trail. “I didn’t have any coordinates, nobody knew exactly where it was,” recalls the missionary-pilot, who grew up in Congo’s remote North Kivu province, the son of another Adventist missionary, and has spent nearly his entire life in Central Africa. “So I’m flying at 500 feet, looking for anything unusual.” As he passed over blackened scrub west of the town of Fianga, the result of a controlled burn to create arable land, Roberts noticed elephant tracks—hundreds of them—in the charred soil. He dipped his plane lower and followed the tracks to a clearing. It was then that he saw the first pile of bones.

Roberts counted the skeletons of between 15 and 20 elephants. The remains were fresh. “You could see the moisture in the ground from blood,” he says. Hungry villagers had already swarmed over the corpses, stripping their meat. Even the animals’ skin was gone, taken to fashion gris-gris, or totems, for animist ceremonies. A few hundred yards from the first site Roberts came upon a second heap of bones—then a third, and a fourth. “Twenty, thirty animals at a time had gone down. It was terrible,” Roberts says. The pilot estimated that 120 elephants had been killed here; the government would later put the total at 86.

The sole survivor of the massacre, Roberts would learn, was a 9-week-old calf, captured by villagers, roped to a tree and taunted day and night by the village boys. Roberts tracked down the location, drove there and loaded the weakened and traumatized orphan into the back of a pickup truck. He then drove several hours to the landing strip where he had parked his Cessna. After an all-night vigil, he used a container of milk to lure the elephant onto his plane, flew to his mission and tried to nurse the calf back to health. “He saw his whole family murdered, then ran around looking for his mother, then was tortured and abused for a week,” says Roberts, who even inserted a tube into the baby’s stomach to force-feed him. “The emotional condition of an elephant like that—it just shuts down.” The elephant, whom he named Max, died after ten days in Roberts’ care

The Sahel, the vast, arid zone that lies between the Sahara and the Sudanese savanna, once supported a population of a million elephants. Nineteenth- and early 20th-century Western travelers wrote with amazement about the huge herds that roamed the bush, and the contests between the great animals and the Baggara Selem, Sudanese horsemen who pursued the herds with ten-foot-long spears. “Among the Selem, several are so dexterous that they can bring the elephant down with a single thrust of the lance,” observed Jules Poncet, a French ivory hunter who joined the chase in the 1860s.

But sport turned into slaughter in the 1970s, fueled by a proliferation of assault rifles from the continent’s post-colonial bush wars. A 1989 international ban on ivory tamped down the bloodshed, but China’s growing wealth and insatiable hunger for ivory—carved into brush-holders, boxes, statuettes and other intricate pieces—has pushed the numbers back up. Six years ago, the Convention on International Trade in Endangered Species, the United Nations body that regulates the international wildlife trade, declared China an “Approved Ivory Trading State”—allowing a one-time legal sale of ivory from four southern African countries, which at the time had large and healthy elephant populations. The sale to China of 62 tons of ivory from African stockpiles in 2008 reopened the door for a vast illicit market—by making the task of distinguishing legal from illegal ivory next to impossible. In Hong Kong, one of the ivory trade’s main transit points, seized ivory rose from 3.2 tons in 2010 to 7.9 tons in the first ten months of 2013—the equivalent of 1,675 dead elephants. Vietnam, Thailand, Taiwan and the Philippines have also become major purchasers of elephant tusks. In December 2012, Malaysian authorities seized 1,000 elephant tusks hidden in secret compartments in two shipments of mahogany from the West African nation of Togo. The 24-ton seizure, worth tens of millions of dollars, is believed to be the largest such haul in history.

Now the Sahel has again become a killing ground. A year before the Fianga massacre, in February 2012, Roberts had also been nearby when 100 raiders on horseback had galloped out of Chad into Cameroon’s Bouba Ndjida National Park, mowing down between 300 and 600 elephants with AK-47s and rocket-propelled grenades. The killers stopped to pray to Allah between barrages of gunfire and played a cat-and-mouse game with the Cameroon army for two weeks before disappearing into the bush. Of the 50,000 elephants that roamed Chad 50 years ago, barely 2 percent are left. In the neighboring Central African Republic and Cameroon, the population may be even lower. Poverty, bribery and insecurity are all contributing factors in a region where a single large tusk can sell on the black market for $6,000—ten times the annual salary of a typical worker. Many conservationists say that if governments don’t do more to protect the remaining herds, the last elephants could disappear within a generation.

“What is special about elephants is just how similar they are to us—socially and developmentally,” says Caitlin O’Connell-Rodwell, a Stanford ecologist who has written four books based on her Namibian field research on elephants. “If you watch a family group reuniting, their behavior is exactly like ours—the little cousins darting off together, the elaborate greetings of adults. Elephants offer a way of looking into the mirror, for better or worse,” she adds. “If we value human rights, we should also value animals that have the same level of sophistication that we do. We should keep those beings with us here on earth.”

When Gary Roberts found this orphaned elephant next to its dead mother, he made an attempt to fly it to safety

Last June, the government of Chad declared a significant victory in its often-faltering attempts to save its most endangered species. The Mobile Brigade for Environmental Protection, directly under the control of President Idriss Déby Itno, captured the alleged mastermind of the March 2013 killings at Fianga and many other massacres. Hassan Idriss Gargaf, 38, was said to command a gang of gunmen who rampaged across the Sahel over the last few years, growing wealthy from the sale of ivory and leaving a trail of dead elephants in its wake. Chad’s minister of the environment issued a press release calling Gargaf a “recidivist poacher,” the “mastermind” of some of the biggest elephant slaughters in Chad’s history and “a pivotal player in the international poaching network.” “He was the worst of the worst,” says Adoum Mahamat Brahim, a park ranger turned regional environmental chief who tracked Gargaf and his accomplices. The rise and fall of Gargaf sheds light on the combustible mix of corruption, desperation and globalization that is fueling the African poaching explosion. It also reflects the dedication of a handful of conservationists, rangers and other environmental crusaders who are determined to bring the killers down.

***

Hassan Idriss Gargaf’s twisted trail begins at Zakouma National Park, founded in 1963 and today one of the Sahel’s last refuges of the elephant. Comprising 1,200 square miles in remote eastern Chad, about 500 miles from Ndjamena, the park lies at the convergence zone where the sandy wastes of the Sahara give way to savanna and tropical rainforest. For five months a year, rainfall submerges most of the park. During the dry season, the residual rain collects in a handful of channels and hundreds of muddy pans, which sustain a vast population of birds and wildlife. “In the rainy season all this is just one big wetland,” park manager Rian Labuschagne told me, as we flew in his Cessna last December over thick riverine bush and acacia-speckled savanna. The landscape was still vibrantly green a month after the last rain. Lotuses clogged milky channels, and ponds glinted silver in the sun. Herds of buffaloes galloped across a grassy plain. As we dipped low over the Salamat River, crocodiles wriggled from the sandy banks into the water. Banking right, Labus­chagne circled over a group of 250 elephants, the largest assemblage I had ever seen. They fanned their ears and raised their trunks like snorkels—an instinctive response to danger.

Gargaf grew up on the park’s northeastern border, in Am Timan, a provincial capital of 75,000 people. It is a sleepy place of herders, cultivators, a smattering of missionaries, and government officials. Beyond the town lies sparsely inhabited bush, where Gargaf—the son of subsistence farmers—roamed in his youth as a guide for hire, leading livestock across ancient cattle trails.

In February 2003, just across the Sudan border in Darfur, two rebel groups rose up against the Islamist government, accusing it of marginalizing the country’s non-Arab population. Sudanese President Omar Hassan al-Bashir unleashed Arab horsemen, known as Janjaweed (a term formed from the Arabic for “man,” “gun” and “horse”), in a campaign of ethnic cleansing against the rebels and their civilian supporters. The Janjaweed raped, tortured and killed thousands and displaced two million, including 200,000 now in displaced persons’ centers and refugee camps in Chad. The Janjaweed financed their operations partly by poaching elephants in Zakouma, a one-week ride from Darfur. The AK-47-wielding horsemen—some direct descendants of the Baggara Selem—shot dead dozens of elephants every month in and around the park, sawing off the tusks and leaving corpses to rot on roads and in the bush.

Chad’s government was preoccupied with a homegrown insurgency; the park manager at the time, a European company contracted by the European Union, was ineffective; corrupt park guards tipped off poachers about the whereabouts of elephants and patrols. In 2008, the head of anti-poaching at Zakouma was fired for selling weapons to the killers. In six years, the elephant population at Zakouma plunged from 4,000 to 450.

Gargaf had learned the migratory routes of elephants from his cattle drives, and when Sudanese poachers approached him with an offer to serve as their guide, he leapt at the opportunity. Gargaf had fathered seven children with two wives, and he might well have felt financial pressure from his family responsibilities. Eventually, Gargaf teamed up with another pastoralist from Am Timan, Yaya Hassap. In 2007, the pair allegedly led Sudanese poachers into Zakouma, where they shot dead two guards, killed 13 elephants and destroyed several vehicles. Eventually the two partners in crime began their own poaching network—purchasing weapons, organizing logistics and finding a regular buyer of tusks in Ndjamena, a merchant known as Mahmadou.

***

Adoum Mahamat Brahim, the gaunt, soft-spoken wildlife expert from Am Timan, had always dreamed of working at Zakouma. As a boy in the bush, he became fascinated by elephant behavior and began doing volunteer patrols on horseback around the park as a teenager. The park put him on staff in 1998, at age 22, the same year that two rangers were killed in an early battle with poachers. Brahim watched, horrified, as carnage swept the park, and as men he had befriended lost their lives in the escalating violence. (A total of 19 park rangers and four military officers have been killed at Zakouma since 1998.) Almost every day he would encounter the corpses of elephants on the main road—shot down by poachers when they emerged from the bush.

Though well armed, the guards lacked radios and had established no intelligence networks. “I was demoralized, but I had to keep working because this was our national patrimony,” the 38-year-old recalled at the park headquarters, a turreted stucco building that resembled a French foreign-legion fort. “Even if there was a single elephant left in Zakouma, we have the duty to protect it.” Brahim’s dedication, say observers, was a rare quality in a field where the main motivation factor is a desire to escape from grinding poverty. “Few of the guards give a rip if these elephants live or die—if you took away their salaries tomorrow they’d stop working,” says one wildlife consultant in Chad who didn’t want to be identified. Brahim is one of those rare guards, says Rian Labuschagne, who are driven by a passion for Chad’s endangered wildlife and a strict code of ethics.

Brahim began cultivating informants in nearby villages, trading small gifts for tips. “Little by little we recovered arms, we got information,” he said. In 2010 he began hearing one name over and over: Yaya Hassap. “I learned that every poacher who comes to this region passes through Yaya,” said Brahim, who began a search for the elusive figure. “He controlled a huge network.”

One day Brahim received a call on his cellphone from a number he didn’t recognize. “I said ‘Who is this?’ The person answered, ‘Yaya.’ I said, ‘Yaya?’ I wondered why he was calling me.” Hassap informed Brahim that he knew the ranger was hunting for him and requested a meeting. In a teashop in a bazaar near Am Timan, Hassap told Brahim about his partnership with Gargaf. The relationship had become strained, he said, because Gargaf had been cheating him on his share of ivory profits. “Yaya was very discontent,” says Brahim. Hassap made an offer: He would lead Brahim to his accomplice in exchange for a job in the park service. The ranger, with the approval of higher-ups, agreed.

Posing as an ivory buyer and arms merchant, Brahim telephoned Gargaf in March 2011. He had AK-47s, M-14 semiautomatics and 3,000 rounds of ammunition for sale. Would he be willing to come to Ndjamena to inspect the merchandise? Gargaf agreed to a meeting, and the commander of the Mobile Brigade provided Brahim with a safe house and weapons. Gargaf arrived in Ndjamena that evening. As he inspected the weaponry, the poacher bragged about killing 26 elephants in a single day at Zakouma in 2010, and about a string of other crimes. “He was very proud of his killing,” said Brahim.“Gargaf told me that he knew the [Zakouma] region very well, and when he realized how profitable [poaching] could be, he got deeper into it, and he found ivory buyers and guns and played a bigger and bigger role.”

At 10 o’clock that evening, Mobile Brigade troops surrounded the house and took Gargaf into custody. Gargaf was imprisoned in a military compound in Ndjamena. As a reward for his work, the government promoted Brahim to chief environmental officer in the Salamat region around Zakouma, an honor for a poor park ranger who had never gone to college. “These jobs are almost never given to someone without an education,” says Labuschagne. “But Adoum has the heart and the guts to do it.” Thanks to one man’s initiative, it seemed—at least for the moment—that Chad’s government had achieved a victory.

***

At Zakouma National Park, where Gargaf, Hassap and their Sudanese gangs had cut a swath of destruction for years, there were similar signs of a turnaround. In 2010, the park’s European Union benefactors, dismayed by the carnage, threatened to withdraw all their financing if Chad’s government didn’t bring in a qualified manager. They turned to African Parks, a South African nonprofit organization. Rian and Lorna Labuschagne, conservationists with decades of experience in Malawi and Tanzania, were brought in to protect the dwindling herd.

The Labuschagnes encountered ubiquitous evidence of slaughter and traumatized survivors. “You found carcasses all over the park when we came here. It was just a killing field,” Rian, the grandson of an Afrikaner missionary in Malawi, told me, as we sat on the terrace of Zakouma’s guest lodge beside the Tinga River at dusk, sipping Castel beers while baboons frolicked in the mango trees. All 450 survivors had concentrated into a single group, a behavior apparently inculcated during the 19th-century spear-hunting days, when bunching together made it harder for the Baggara Selem to isolate the weak. But now the animals’ behavior was accelerating their destruction. “It made it easier for poachers to shoot them,” said Rian. One of the first things they noticed was an absence of calves. “They had stopped breeding because of the constant shooting at them, the stress, like humans in a war situation,” Rian said. The elephants panicked at the sight of horses, the poachers’ main means of transport. Early on, an elephant bull charged a ranger on horseback when he felt threatened; the horse bolted and threw off its rider, who was projected headfirst into a tree trunk. He later died.

The Labuschagnes fired guards suspected of taking bribes, spent $100,000 on radios and GPS devices, and set up solar-powered systems and repeaters for the park’s radio network. They built ten airstrips on the periphery of the park and converted two old ones inside Zakouma into all-weather airstrips. They set up trailers stocked with food and other supplies to facilitate patrols during the rainy season, when Zakouma becomes impassable by road. They darted and collared elephants to keep better track of their movements. The Labuschagnes changed patrol positions daily and didn’t tell rangers where they were going until a few hours before they were deployed. “This eliminated the chance of information going out to the wrong people,” Rian said.

The poachers struck back hard. In August 2012, at the height of the rainy season—when some elephants leave their sanctuary and follow ancient migratory routes—Sudanese poachers killed six elephants near Heban, 60 miles north of the park. A ranger squad from Zakouma discovered the poachers’ deserted camp and seized satellite phones, solar panels, medicine, food, 1,000 rounds of ammunition and Sudanese military ID cards. Three weeks later, the poachers crept up on six rangers in the middle of dawn prayers and shot them all dead. “The cook survived and told the story,” said Rian. “We got there three days later and found their bodies.”

Sudanese troops captured one of the attackers and turned him over to Chadian authorities, who locked him up in Am Timan prison. But the warden allegedly smuggled in weapons in exchange for a bribe, and in August 2013, twenty-six prisoners, including the Sudanese poacher, broke out and disappeared. “He murdered six of our guards and he just walked free,” Babakar Matar Breme, Zakouma’s assistant park manager, told me bitterly. Casting a glance at framed photos of the six dead rangers on the wall of park headquarters, Brahim told me, “There is no justice in Am Timan. People there are always ready to take money and let the poachers escape.”

***

Weeks after his arrest, Gargaf, too, escaped from custody—walking out unchallenged from the military barracks in Ndjamena. “He came and went, he was well taken care of. One day he didn’t come back,” Brahim says with disgust. Now he was back in operation along the Chari River flowing through farmland south of Ndjamena. There were no game wardens or sanctuaries in this more fertile, populous corner of the country, but there were about 200 elephants. Subsistence farmers, angered by beasts trampling their crops, were often happy to collaborate with poachers. Gargaf and his gang murdered 63 elephants in August 2012 along the Chari and 40 elephants along the Chad-Cameroon border in an attack in which five Cameroonian forestry agents died.

The Cameroon army captured the poacher again in 2012. Gargaf again got away. A few months later came the massacre of the 86 elephants near Fianga. Brahim traced Gargaf to a new base in Goré, in southernmost Chad, beside the Central African Republic border. “I told my informant there, ‘If it’s day or night, it doesn’t matter, if you see Gargaf returning home, you call me,’” Brahim said. Then, last June 14—hours after the informant tipped off Brahim that Gargaf was back—a Mobile Brigade force broke down the door of Gargaf’s house and placed him under arrest. Interrogated after his capture, Gargaf maintained that he was just a small-timer. “I’m not hiding anything,” he told his interlocutors. “I’m a cattle trader...hired by poachers to guide them in their operations, for which they offered me one million francs [$2,500]. It was a proposition that I found much easier than trading cattle.” Gargaf admitted only to helping his group kill ten elephants around the Chari River, “and after they dispersed, I went back to herding cattle.”

***

A few months after Gargaf’s third arrest, I joined Rian and Lorna Labuschagne on a game drive through Zakouma to observe the progress they had made in stabilizing the onetime war zone. At midday, the best time for observing elephants in the wild, we climbed into a roofless Land Cruiser, laden with ice chests full of water, a GPS system and a hand-held beacon that would home in on signals emanating from several collared animals. As we turned off the road onto trackless savanna, a single-engine Cessna circled above, trying to help us by spotting the beasts from the air. We bounced over a field of dried mud, an impassable swamp during the rains, and negotiated around stands of tamarinds and seyal acacias. Buffaloes and small antelopes disappeared into the foliage just ahead of us.

Rian, at the wheel, tried futilely to raise the pilot, but he was on a different radio frequency. He then attempted communicating with him through the radio room at headquarters. “La base la base la base la base?” he intoned, in Afrikaans-accented French. He got no response. The park manager was growing frustrated. He made a few disparaging remarks about the park’s radio equipment and plowed on through the bush.

The heat was fierce, and there were still no signs of elephants. The Cessna continued to circle above us. Then Lorna, in the truck bed, picked up a faint signal. “They must be there, to our right,” she said. Rian plunged the 4x4 into a thicket. Slender acacia trunks bent and broke beneath the Land Cruiser, and needle-studded branches swung close to our heads. “It’s getting louder,” Lorna said excitedly.

We entered a field of tall elephant grass. Soon we were lost in a jungle of ten-foot-high stalks, unable to see a foot in front of us. But the signal was loud now—and up ahead, I saw a flash of movement. I heard a rustle in the reeds, caught a glimpse of gray, and then, through the sea of yellow, I glimpsed a massive bull. “Elephants!” Lorna proclaimed.

Rian pulled the car over and advanced on foot. I followed right behind him. We moved carefully through the grass, trying not to alarm them. The bush came alive with sound and movement—the rustling, munching and jostling of 250 elephants. We had come across the largest group, Rian whispered in satisfaction, maneuvering for a better vantage point. They were still mostly obscured behind the veil of grass, but I could make out individuals—a frolicking adolescent, a protective mother and her 2-year-old, a massive alpha male. Then, as we got to within 25 yards of the herd, the bush erupted in a chorus of trumpets. The blaring horns of dozens of elephants were accompanied by a strange, low vibrato—an elephant purr. I froze, unsure what to do. Was the cacophony meant as a warning for us to retreat? Rian shook his head and motioned for me to stay. He guessed, he whispered, that two groups of elephants had just crossed paths—and were simply saying hello.

The group moved en masse, marching through the grass toward a muddy pan. Rian and I hung back as the animals—like children jostling for space at a playground water fountain—crowded around, splashed and sucked the pool dry. A mud-covered teenager turned to face us, fanned his ears and raised his trunk in a gesture of annoyance, then turned awkwardly around and plodded off to join his kin. We followed them to a clearing, where we had an unobstructed view of the entire herd. The huge procession moved in a single line across the savanna. On and on came the elephants, an unbroken line of power and majesty.

“Look, there’s a calf,” Rian said excitedly, pointing to an infant sheltering behind its mother. It was one of 21 born in the last year, Lorna would later tell me, another encouraging sign of stability—the longest period of peace at Zakouma in decades. “We say our aim is to get Zakouma back to 1,000 elephants,” he said, as we drove back to headquarters in the fading light, exhilarated by our hour-long encounter.

The Labuschagnes guess that if all stays on course, they could achieve that number in a decade. One hopeful sign for them is a widening crackdown by governments against the black-market ivory trade: In January 2014, Chinese authorities destroyed more than six tons of confiscated ivory ornaments and tusks in Dongguan, a city in the southern province of Guangdong, a center for ivory smuggling. The destruction by China, the first ever by that country, follows the destruction of six tons of ivory in the United States in November 2013.

At Zakouma and along the Chari River, meanwhile, the battle against poaching goes on—though it is often hard to tell just who is winning. Some time before my arrival at Zakouma, the ranger staff appeared to have achieved another big success. After three elephants were killed near the park, Hassap, the criminal-turned-guard, had led a raid on a poachers’ camp that netted a trove of weapons and ivory. Hassap even brought back a photo of the corpse of a poacher killed in the attack, and collected $10,000 in reward money. But it soon emerged that Hassap had faked the raid and staged the photo, using his brother to play the corpse. Fired from his job as a ranger, he is currently in jail awaiting trial. “He just played a game with us,” said Brahim in disgust. Other guards have been suspended pending an investigation into their role in the fraud.

As for Hassan Idriss Gargaf, the master poacher’s whereabouts are difficult to ascertain. Is he, as some Chadian officials insist, locked inside Korotoro Prison, a notorious Saharan fortress surrounded by barbed wire, cited in a 2012 Amnesty International report for overcrowding, filthy food and water, poor sanitation, lack of health care, and extrajudicial killings? Or is he, as skeptics maintain, at this very moment lying in wait in a thicket of acacias, Brahim’s nemesis poised again to unleash carnage on the scale that Gary Roberts discovered near the Cameroon border a year ago? “If Gargaf has escaped again,” Brahim told me, as he stood with his comrades in front of Zakouma park headquarters, “it doesn’t make any sense for me to continue in this job. It would be an outrage.”