The afternoon of January 11, 1941, was sleepy and quiet at the fort deep in the Sahara in Italian-occupied Libya, in an oasis called Murzuq. Though their comrades back home were embroiled in the Second World War raging across Europe, the Italian soldiers guarding this outpost, a strategic road junction, felt comfortably distant from the battle. As far as they knew, the closest enemy was hundreds of miles away, in British-controlled Egypt. Murzuq’s defenders were so relaxed, some of them were outside the walls for an after-lunch stroll.

Out of nowhere, a column of military trucks and jeeps came roaring toward the fort, spitting machine-gun fire. The invaders—British, French, and New Zealander troops—split into two groups. One hammered the compound with mortars and machine-gun fire, while the second raced toward a nearby airfield. Before most of the aerodrome defenders had time to reach their weapons, the commandos overran them. The Allied troops leaped from their vehicles, dashed into the hangar, poured gasoline over the three bombers inside, and set them ablaze. Snatching up several Italians as prisoners, the strike force sped away, disappearing into the Sahara.

You can’t blame the Italians for having let down their guard. The attack seemed impossible. How could nearly two dozen enemy vehicles have traveled, undetected, across all those miles of rock and sand?

That night, from a remote desert camp, the Allied soldiers—­members of an elite squad known as the Long Range Desert Group—related news of the assault via a wireless transceiver to British headquarters in Cairo, Egypt. There, Ralph Alger Bagnold, a tall, sinewy British army lieutenant colonel, received the report with satisfaction.

Bagnold had founded the Long Range Desert Group the previous year, and had handpicked and trained its soldiers. It was his unmatched skills as an explorer of the Sahara that had made it possible for the commandos to travel through the trackless wasteland for the 16 days it had taken to reach Murzuq. Bagnold, a rare combination of soldier and scientist, understood the desert better than any European alive. He had not only devised the techniques and innovations that allowed cars to drive atop oceans of sand, but he had also unraveled the mystery of how the grains of sand themselves move. His career already included action in two different world wars. He couldn’t have known at the time, but one day it would range across two different worlds.

Bagnold was born in 1896, in Devonport, England, to a genteel family with a long tradition of military service. His father had fought in some of Great Britain’s colonial battles in Africa but served mainly as an engineer. Conversant with carpentry, metalworking, and other trades, he was known for being able to make, fix, or jury-rig just about anything, skills he passed on to his son. Young Ralph started studying engineering at age 13. Scorning football and cricket, he spent his afternoons learning to use lathes, ­metalworking tools, and milling machines.

By the time he was 19, in 1915, Bagnold was a second lieutenant in the British army and enrolled in its venerable military engineering school. “We learned a great deal that was lastingly useful—how to dig almost effortlessly, how to lift and move great weights with rope and pulleys, a bit of surveying and mapmaking, and how to destroy with explosives,” Bagnold wrote in Sand, Wind and War, his 1990 autobiography. “Still more important, we learned to improvise.”

He also learned to design battle trenches, and soon found himself fighting in them. Sent to France in World War I, Bagnold served on the front lines of some of its most brutal battles. “There was always some poison gas around from German shells,” he recalled with trademark British reserve. “Sometimes we had to don our clumsy masks, but usually we just coughed our way through.”

In the mid-1920s, the army posted Bagnold to Egypt. The desert entranced him—its immensity, its mystery, the alluring fact that so much of it was unknown. “In Cairo we had at our very doorstep the edge of a vast field for real exploration,” he wrote in his memoir. The eastern Sahara is “the most arid region on Earth, waterless and lifeless save for a few artesian oases scattered several hundred miles apart.”

Bagnold’s peers told him the sands couldn’t be crossed in a motor vehicle. “This struck me as an irresistible challenge,” he recalled. Peace-time soldiering allowed him plenty of time to explore. With friends, he started venturing into the wastelands with the sturdiest machines he could find, Model T and Model A Fords. The group ranged around eastern Egypt, the Sinai, what was then Transjordan and Palestine, and finally into the Sahara itself, penetrating deeper than any European had ever gone.

Ford had not designed its cars for this kind of off-roading. So ­Bagnold, with plenty of trial and error, devised a series of modifications that allowed his crew to drive in sand, and to survive for weeks at a time in the parched terrain. To conserve water for the cars, Bagnold soldered pipes onto the radiators to capture escaping steam, which collected into a metal can, condensed, and recirculated. Because the magnetism of the vehicles’ ample metal and moving parts threw off conventional compasses, Bagnold navigated by bolting a sun ­compass onto the dashboard. To cut down weight, he stripped off bumpers, hoods, and windshields, and even replaced portions of the car bodies with wood. Knowing the unholy beating the elements would inflict on the vehicles, the explorers didn’t just pack spare tires; they practically packed spare cars. Every few days they spent hours patching rubber by hand, or swapping out damaged epicyclic gears and suspension springs.

During these years of experimentation, Bagnold drove some 20,000 miles, much of it in trackless territory. Of course, the cars also got stuck. To cope, Bagnold used perforated steel “channels”—essentially, portable ramps—and canvas-and-rope mats to lay under the wheels to gain traction. They worked but with tremendous effort: “At one moment you would be doing a steady thirty miles an hour to the reassuring whine of the tyres; the next halted dead in five yards with the car up to its axle in a dry ‘quicksand,’” wrote one of his traveling companions, William Boyd Kennedy Shaw, in his memoir Long Range Desert Group: Behind Enemy Lines in North Africa. “Using sand channels and sand mats, and with a dozen sweating and cursing men, the truck would be extricated two yards at a time.”

He and his friends might have been in it for the adventure, but Bagnold became fascinated by the titanic dunes and the tiny grains that formed them. In the desert, he later wrote, “instead of finding chaos and disorder, the observer never fails to be amazed at a simplicity of form, an exactitude of repetition and a geometric order unknown in nature on a scale larger than that of crystalline structure. In places vast accumulations of sand weighing millions of tons move inexorably, in regular formation, over the surface of the country, growing, retaining their shape, even breeding.”

How, he wondered, did the dunes keep their shape while traveling? Why did sand accumulate on them instead of spreading out? How did the individual granules move? Geologists had studied the origins of sand, and engineers used empirical techniques to predict sediment flows, but no one had applied the principles of physics to explain the movement of the grains.

After retiring from the army and returning home, Bagnold set out to be the first. Ever the improviser, he built a wind tunnel out of plywood and glass and set it up in borrowed space at Imperial College London. “I felt it was really just exploring in another form,” he later reminisced. Using his practical knowledge of physics, mathematics, and engineering, he ran hundreds of sand samples through the tunnel. He recorded and photographed the ways in which wind at varying strengths moved different-size grains, and how the grains interacted on the ground and in the air.

He found that as winds lift sand into the air, the grains affect the wind’s movement. And as the wind’s movement of sand changes the shape of the desert floor, that shifting surface affects how both move. Among Bagnold’s key discoveries was that windblown grains jump, a movement known as saltation: They briefly rise into the air, crash back to the ground, and bounce up again. In the process, they can transfer energy to larger grains on the ground, nudging them ­forward in a process called surface creep.

To describe these movements, Bagnold developed mathematical formulas that he later checked against real-world conditions in the Egyptian-Libyan desert during a return trip there in 1938. At one point, he lost his goggles. “I spent some very uncomfortable hours sitting in the open, directly exposed to a violent sandblast, trying to keep my eyes open while taking readings from an array of gauges and sand traps,” he recalled in his memoir. “The purpose of eyelashes was very evident.”

After five years of research, he had enough data to write a book, The Physics of Blown Sand and Desert Dunes. It was the first scientific investigation of the subject, and is considered a foundational text in the study of aeolian, or wind-driven, processes. “His book was seminal,” says Haim Tsoar, a leading expert in the subject at Israel’s Ben Gurion University of the Negev. “I think he was a genius.”

But before the book could be published, World War II broke out. Summoned back to the army, Bagnold found himself once again in Egypt. There, Britain’s troops faced off across the Sahara against a larger Italian fascist force in Libya. Examining maps of the region, Bagnold realized that his eccentric hobby could be converted into a practical weapon.

In 1940, with Italy plainly preparing to invade Egypt from Libya, Bagnold pitched the British commander, Gen. Archibald Wavell, on his idea: a specially trained, fast-moving commando force that could strike from deep in the desert. Wavell was sold. He gave Bagnold a free hand to sow whatever havoc he could in Libya. Bagnold recruited volunteers, ransacked military warehouses, and rummaged Cairo junk shops for his unconventional needs: sandals, Arab headdresses, trouser clips to hold down wind-tossed maps, and lots of spare tires.

Bagnold took a small fleet of Chevrolet 1.5-ton trucks and outfitted them with his sand channels, sun compasses, and other innovations. He cut off windshields, installed extra-strength springs, and mounted Bofors anti-aircraft guns on their beds. He organized teams into 30-man units. “These patrols had to be completely self-­contained for long independent action, out of reach of any possibility of help,” ­Bagnold told a radio journalist in 1941. “Each needed to be an army in miniature.”

A typical patrol comprised around 10 trucks and jeeps. One truck carried communications and navigation gear. Another toted heavy weapons. The rest carted fuel and supplies. The LRDG’s raids became legendary; even today the group has many fans, foremost among them Jack Valenti, founder of the ­California-based Long Range Desert Group Preservation Society. Valenti and his comrades have spent numberless hours and tens of thousands of dollars researching and re-creating the LRDG’s trucks and jeeps. He and a few friends showed off one of them at a convention of military-vehicle enthusiasts in Northern California this past April. The roofless 1.5-ton Chevy truck, built in the early 1940s, was fitted out with rolled-up canvas sand mats clamped to the front bumpers, and perforated steel sand channels—the ramps to put under stuck wheels—lashed along the sides. A sun compass was bolted to the wooden dashboard. The uncovered cargo bed was neatly packed with spare parts, medical gear, wooden crates for ammunition, and canvas bags of rations, including cans of Libby’s corned beef, an actual brand Bagnold’s men ate. “Bagnold was a brilliant man,” says Kevin Canham, a snowy-bearded former high school teacher, Navy vet, and preservation society member. “He was the World War II version of Lawrence of Arabia.”

In fall 1940, Bagnold’s LRDG, made up of a few old comrades plus 150 New Zealand volunteers, rode into action. Camouflaged amid the dunes, they spied on enemy troop movements, radioing their intelligence back to British forces in Cairo. They launched lightning surprise raids on Axis garrisons and airfields, then vanished back into the expanse of the Sahara. They cultivated a desert-pirate look, sporting Arab headdresses, unkempt beards, and a scorpion insignia, to the excitement of the press back home.

Their impact belied their size. One year after the LRDG took to the field, Wavell wrote in a dispatch: “Not only have the patrols brought back much information, but they have attacked enemy forts, captured personnel [and] transport and grounded aircraft as far as 800 miles inside hostile territory. They have protected Egypt and the Sudan from any possibility of raids, and have caused the enemy…to tie up considerable forces in the defense of distant outposts.”

In July 1941, at age 45, finally weary of the heat and harsh living conditions, Bagnold handed over the LRDG command and took a post in Cairo. The group fought on until the Axis was defeated in Africa in 1943. It went on to missions in Greece, Italy, and the ­Balkans before disbanding at the war’s end.

With peace, Bagnold returned to England, married, had two children, and settled down in rural Kent. His career as a desert fighter was over, but he was about to launch a new vocation as a desert expert. His work on the physics of windblown sand had, to his astonishment, gotten him elected a Fellow of the Royal Society—one of Britain’s premier scientific honors. “It was more surprising because I was merely an amateur scientist with no academic standing,” he wrote in his memoir. There was an upside to that: “Being an amateur, a free lance who never held any academic post or had any professional status, I had the rather unusual advantage of considering problems with an open mind, unbiased by traditional textbook ideas that had remained untested against facts.”

Bagnold’s knowledge proved valuable. Oil and gas companies building installations in the desert sought him out for help understanding how to cope with the ever-shifting sands. He advised British Petroleum on building a pipeline across a huge swath of desert in Libya, and explained to oil executives in Iran the basics of how sand moves and how to build fences to keep it out.

But Bagnold devoted most of his energy to research, turning his attention to the study of how rivers transport sediments, a field in which he also made important contributions. His 50-years-long ­creative and interdisciplinary approach to sediment physics “enabled today’s earth scientists and engineers to plan and pursue projects equipped with a deep, if still imperfect, understanding of these critical natural processes,” wrote the late geologist and fellow arenophile Michael Welland. Bagnold authored nearly 50 scientific papers and racked up prestigious awards from the National Academy of Sciences and the Geological Society of America, as well as two honorary doctoral degrees. Still, “he was extremely modest,” says his son, Stephen Bagnold. “Nine-tenths of him was always hidden.”

Bagnold’s career could have ended with World War II, and he would still be assured a place in the history books. But there was one more phase to come. In the 1970s, NASA called. It wanted him to apply his knowledge of earth science to another planet. The agency’s first Mars orbiter had spotted what appeared to be not only sand, but dunes. It wanted Bagnold to help it understand these formations. On Mars, says Bethany Ehlmann, a research scientist at NASA’s Jet Propulsion Laboratory, “there are the same physics but with totally different constants of gravity, grain density, and atmospheric pressure.”

For several years, Bagnold worked with the agency, including co-­authoring a paper with Carl Sagan. “I spent one evening at a McDonald’s with a small group of young scientists from NASA’s Jet Propulsion Laboratory in Pasadena,” Bagnold wrote later in his autobiography. “It was fascinating for an old man of eighty-one to listen to their casual talk of navigating a spacecraft two hundred million miles away as easily as an aeroplane. Man had not begun to fly at all when I was born.”

Almost until the end of his life, the old soldier-scientist stayed active, publishing his final papers—one, oddly, includes an analysis of the random distributions of word lengths in different languages—in the 1980s. His last paper appeared in 1986, when Bagnold was 90 years old. He died four years later.

“He’s still very much present in the modern field,” Ehlmann says.

She should know. Over four months, beginning in late 2015, ­Ehlmann helped lead NASA’s Curiosity rover on the first exploration of a dune field conducted on another planet. The rover uncovered important information on the history of the Martian landscape and the chemistry of its components. In honor of the man who “revolutionized our understanding of aeolian processes on Earth,” as ­Ehlmann put it in a recent paper on the mission, her team bestowed a fitting name on the formations. Millions of miles from the nearest human habitation, the remotest desert ever explored by a man-made vehicle now includes an area known as the Bagnold Dunes.

Vince Beiser is the author of The World in a Grain: The Story of Sand and How it Transformed Civilization.

This article was originally published in the Fall 2018 Tiny issue of Popular Science.

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