Along the U.S-Mexico border, temperatures in summer hit triple digits daily. The Sonoran Desert straddles the border, creating a deadly barrier to the thousands of migrants seeking a better life in "el Norte," the North. Untold thousands of people have died in these deserts, following the path known as "el Camino del Diablo," the Devil's Highway. How many have died, we will never know, as the desert erases evidence of those who fall there; vultures, coyotes and insects quickly set upon the corpses, leaving only bleached bones. The remains of over 3,000 people have been found, yet experts estimate over 10,000 have died while attempting to cross. Several volunteer groups have for years been plying the hot sands of the Sonora, leaving food, water and medical supplies along known migrant trails, doing what they can to limit the lethality of the desert.

In January 2018, Scott Warren, of the humanitarian aid group No More Deaths/No Mas Muertes, was arrested and charged with harboring "aliens" and conspiracy, federal crimes for which he faced 20 years in prison. The first trial ended in a hung jury, with eight of the 12 jurors voting for acquittal. Federal prosecutors dropped the conspiracy charge and are moving ahead with his retrial, scheduled to begin in November. He still faces 10 years in prison.

We recently traveled on a "water drop" with Warren and two other No More Deaths volunteers, Geena Jackson and Paige Corich-Kleim. We left from the new humanitarian aid office that No More Deaths shares with allied groups in Ajo, Arizona, and traveled along a rough gravel road to onto the Organ Pipe Cactus National Monument. It was still early morning, but the temperature exceeded 100 degrees. Organ Pipe runs from near Ajo all the way to the Mexican border. West of the national monument is the Cabeza Prieta National Wildlife Refuge, the largest refuge in the lower 48 states. "I can't set foot into the refuge right now, because of the misdemeanor charges that I face related to the provision of humanitarian aid," Scott Warren told us.

The increasingly militarized enforcement at border towns like Nogales, Arizona, drives migrants deeper into the desert. "Migrants have been forced out into these remote and rugged areas ... as a result of prevention through deterrence," Warren told us as we stood outside a Customs and Border Patrol forward operating base in the Growler Valley. The Growler Valley is a vast, desolate stretch of sunbaked, cactus-studded earth, running north from the border through Cabeza Prieta and Organ Pipe, then into the Barry M. Goldwater Range, an active military bombing range that migrants must cross in order to reach Interstate 8 and their hoped-for life beyond.

The death of 14 migrants in this valley was eloquently detailed by Luis Alberto Urrea in his Pulitzer-finalist 2004 book, "The Devil's Highway." Urrea describes the six stages of approaching death: "The desert's air, like you, is thirsty. It's sucking up your sweat as fast as you can pump it, so fast you don't even know you're sweating ... the air comes to your lips and pulls water from you. Every breath dries out your nose, your sinuses, your mouth, your throat. ... Desolation drinks you first in small sips, then in deep gulps." Urrea adds, "If you cry, you make an infinitesimal investment in your own death."

Because of the pending trials, Warren accompanied the water drop, but did not engage in the activity personally. "Humanitarian aid is never a crime," Geena Jackson told us. "It is a humanitarian imperative to try and ease the death and suffering in this area ... regardless of government agencies trying to prosecute humanitarian aid workers." She and Paige Corich-Kleim wrote messages on each of the gallon jugs they left in the shade of a tree, alongside a path created over the years by people making this dangerous journey.

"I usually write religious notes, like 'Vayan con la fuerza de Dios' or 'Que Dios bendiga su camino,' which means 'Go with the strength of God' or 'May God bless your journey,'" Corich-Kleim told us, to let the travelers know that the water was not left as a trap by Customs and Border Patrol. They also leave cans of beans to provide calories and life-sustaining salts that people lose in the searing desert heat.

Watching his colleagues, Warren said: "I'm just noticing the energy of this moment, and I think maybe because all of us are here, and hearing here my friends describe the messages that they're writing on the bottles. It's so routine for us that we do this, but even I forget how important and how beautiful and sacred it is."

(c) 2019 Amy Goodman and Denis Moynihan • Distributed by King Features Syndicate