It was mid-spring when residents of the wasteland behind Guadalajara’s international airport noticed a dog roaming their community with a strange object in its mouth: a human forearm. Search teams in the ramshackle neighbourhood of La Piedrera entered a roofless red brick shack flanked by trees decked with bright orange mistletoe. Under several layers of dusky earth they made an even more grotesque discovery. “There were 26 of them here. We found them wrapped in plastic sheets,” said Guadalupe Aguilar, a local human rights activist, as she stood beside the shallow grave. “And they’d thrown something on them – acid or something – because it hadn’t been long [since their murders] and the bodies were already in a real state of decay.” Aguilar, 63, said there were dozens of such clandestine burial sites across Jalisco state, a sun-scorched slice of west Mexico that is paying an increasingly nightmarish price for its pivotal role in North America’s multibillion-dollar drug trade. “This is all about organized crime,” said Aguilar, who spends her life locating and excavating Mexico’s 21st-century killing fields in search of the victims. “Why? Because one person couldn’t do all this on their own.” Aguilar, whose activism forces her to travel with armed guards, did not specify which group’s killers were responsible for the bloodbath in La Piedrera. A crimson handprint on one of the hovel’s walls provided a chilling reminder of organized crime’s capacity for carnage. But authorities say the area, like increasing swaths of Latin America’s second largest economy, is controlled by the Cartel Jalisco Nueva Generación (Jalisco New Generation Cartel), a criminal behemoth now considered Mexico’s most indomitable mafia firm. Less internationally famous than the Sinaloa cartel of the now jailed Joaquín “El Chapo” Guzmán, the Jalisco organization is notorious at home for displays of ultraviolence and military might that experts say pose a growing threat to Mexico’s nationalist president, Andrés Manuel López Obrador. Last June, Jalisco gunmen launched one of the most brazen assaults in decades: a pre-dawn attempt to assassinate Mexico City’s security chief that underlined how López Obrador’s pledges to “pacify” Mexico have gone unfulfilled. Last month came another reminder of the cartel’s punch: the body of a key defector, El Cholo, was dumped on a park bench in Tlaquepaque, a tourist town near Guadalajara famed for its pottery and mariachis. A white-handled kitchen knife had been used to pin a warning to the black body bag. “El Traicionero,” it read. “The Traitor.” The security specialist Eduardo Guerrero said authorities north and south of the US border now considered the group a national security threat. “They have huge amounts of money, the latest generation weapons, military-style paramilitary groups and vehicles … and they represent a very severe challenge to the [Mexican] government – above all in small and mid-sized cities where a detachment of 50 cartel operatives can obviously defeat any local police force.” The official telling traces the Jalisco cartel’s birth to July 2010 when troops killed Ignacio “Nacho” Coronel – the gangster credited with founding Mexico’s methamphetamine trade – in the state capital, Guadalajara. Coronel’s elimination – which the Drug Enforcement Agency (DEA) called “a crippling blow” to the Sinaloa cartel he represented – caused a local rupture that paved the way for the emergence of a new group taking the name of Mexico’s seventh biggest state. But one underworld yarn suggests the split actually began three years earlier, in 2007, when one Guadalajara narco spilled a glass of hibiscus tea over a rival during a gathering in the city’s east. The apparently mundane incident reputedly prompted a bloody and bewildering sequence of betrayals, gun battles and massacres which eventually saw one group prevail. That group was led by Nemesio Oseguera Cervantes – or El Mencho as most know him – a former police officer who is now the DEA’s top Mexican target. For his capture it offers a record $10m reward. Unlike El Chapo, who sought Sean Penn’s help to turn his criminal life into a Hollywood blockbuster, El Mencho prefers the shadows. Few photographs of him exist. His biography, which includes a stint working illegally in the US in the 1980s, is mostly a blur. El Mencho is thought to live hidden in the mountains of south Jalisco – but when troops tried to capture him there in 2015 it ended badly, with cartel killers shooting down an army helicopter with a rocket launcher. “Would I recognize him in a restaurant? No, I don’t think so,” said one underworld observer who asked not to be named. “El Mencho’s leadership is indisputable [but] he’s discreet. He has his bastion of control in the south of Jalisco. Nobody touches him. Nobody messes with him. He’s happy.” The source claimed El Mencho, thought to be in his mid-50s, was known for being simpático and having a good repertoire of jokes. “But also very explosive,” they added. “Veeeery explosive.” Few understand the cartel’s powers better than residents of the Sierra de Ahuisculco, a mountain range to Guadalajara’s west where it runs paramilitary-style training camps and secret laboratories that produce vast quantities of synthetic drugs to traffic north to the US. The area’s proximity to two Pacific ports, Manzanillo and Lázaro Cárdenas – through which precursor chemicals are smuggled in from China – has made it a strategic location. A resident of one small town in the Sierra described how cartel gunmen in black combat gear with the group’s initials stamped on to their bullet-proof vests often swept through its streets in high-end 4x4s, some with mounted machine guns. “You’re afraid to go out at night. You’re afraid to go out with your kids,” complained the resident, who asked not to be named. Guadalajara has long been one of the most important addresses in the Mexican drug business. Infamous cocaine and marijuana barons lived here during the 1980s. By 2008 US officials considered Jalisco’s capital a methamphetamine hub they called “Chemical City”. The Sierra de Ahuisculco has also long been a haunt for drug lords, whose high-level political connections allow them to avoid capture and thrive. But in the last six years residents said the violence had become intolerable. “I’ve never lived through a civil war – but I think this is what living through a war must be like,” said one. “You live in fear. You live in uncertainty. I know three or four people who have vanished. Everyone here has lost someone.” In 2019 138 bags stuffed with human remains were dumped in a nearby forest. “We see it and we do nothing because we know exactly what will happen if we do,” said another local. The violence and the cartel’s struggles with rivals have also taken a horrific toll on Jalisco’s capital. Celebrated as one of Mexico’s most dynamic and culturally rich cities, Guadalajara has simultaneously become a place of almost incomprehensible cruelty and grief. “We’ve been experiencing tough times because criminal groups have been trying to destabilize our state and create an atmosphere of terror,” Enrique Alfaro, the Jalisco governor, said last month as hundreds of troops arrived, supposedly to combat the violence. A few weeks earlier his 46-year-old predecessor, Aristóteles Sandoval, had been shot dead in a restaurant toilet in a meticulously planned hit many suspected was the work of Jalisco assassins. Each Wednesday, desperate mothers, wives, sisters and daughters gather outside the city’s forensic institute seeking news of loved ones. “It’s the sisterhood of pain,” said the group’s 50-year-old leader, Martha Leticia García, as they waited to examine images of body parts unearthed from an ever-growing network of mass graves. García, whose son César Ulises disappeared in 2017 and has not been found, described the macabre routine of such relatives as they sifted through excavated remains for those they had loved and lost. “You see these things up on the screen and say to yourself: ‘That arm looks sort of familiar, that head.’ It’s just so terrible – the viciousness that we’re seeing in this state,” she said. Nearby stood Cecilia Flores, 54, whose 28-year-old son, Wilians, was taken in 2019. Four months later officials told her some body parts had been recovered from a notorious torture house called El Mirador. “They found a hand, his torso and forearm. I’m still missing the other hand and his legs,” she said.