Greg Nichols

The Frogmen


Christian Lambertsen invented the gadgets. Then he suited up and helped save the world. 

Greg Nichols


pre-publication draft

not for Wide circulation


Six men climbed out of the submarine Sciré and into the inky water a mile off the coast of Egypt. It was the dead of night, and the only sound was the lapping of small, wind-tossed waves. Wearing stripped-down versions of a primitive SCUBA device known as the Davis Submerged Escape Apparatus, the men boarded slow-moving piloted torpedoes, which they pointed toward neutral Alexandria Harbor. It was the early days of WWII, and these men, members fascist Italy’s elite Gamma Group, were about to stun the world.

Before proceeding into the harbor, the men stopped momentarily on the surface for a belt of brandy. Then the two-man units submerged and separated to predetermined targets. One of the groups, led by Luigi Durand de la Penne, headed for the anchored British battleship HMS Valiant. Water visibility was poor under the night sky. The manned torpedoes, which carried a detachable explosive warhead and chugged along at three knots, were cumbersome and prone to malfunction. True to form, the motor on de la Penne’s torpedo quit en route to the target and sank in 17 meters of water. Undeterred, he and his partner, Emilio Bianchi, began pulling it along the bottom. When Bianchi lost consciousness briefly, forcing him to surface, de la Penne finished the job alone.

After what seemed an eternity toiling in the silt and near-darkness, a giant shadow eclipsed the trickle of moonlight above. De la Penne made out the massive steel hull of the Valiant. He set the timer on the torpedo’s explosive charge. Then, having pushed his breathing equipment well past its normal operating limits, he swam to the surface, where he was promptly captured by British naval personnel.

In a demoralizing turn, he was placed below deck aboard the ship he had just mined. Bianchi was there, too. Not long before the warhead was set to detonate, de la Penne summoned the captain and told him to evacuate his crew. The captain demanded to know the location of the mine, but de la Penne refused. Hoping to induce them to talk, the captain left the two men aboard during the ensuing evacuation. The explosion came a few moments later and sank the Valiant in shallow water. Still below deck, both Italians survived, their pride intact.

That night, with no loss of life on their side, a skeleton crew of Italian swimmers relying on bare bones technology grounded two battleships—the HMS Queen Elizabeth was the other—destroyed an oil tanker, and inflicted heavy damage on a third battleship. All the swimmers were captured due to the limitations of their equipment, but they had proved the devastating effectiveness of a new kind of warfare.

Pearl Harbor had pulled America into the conflict just days earlier, but American and British intelligence had been working together for months and understood the threat the Italian swimmers posed in the fast-escalating sea war. Behind closed doors, the Italians’ capabilities were deeply troubling. But the strategies they had revealed were tantalizing to a small group of outsiders within a secretive organization called the Office of Strategic Services—later, the CIA. In 1942, with no support from military commanders, who found the notion of sending soldiers underwater fanciful, if not foolhardy, a handful of men relegated to an overlooked branch in the catch-as-catch-can OSS began discussing the idea of creating a team of underwater commandos—elite units that would far surpass the Italians’ capabilities. There was no precedent in American military history for what they had in mind, and there was a problem: the technology to pull it off didn’t exist yet.

Or so they thought.


The medical student was putting the finishing touches on his note: “I will be able to go to Washington any time you suggest. As one of my professors put it, I do not intend to let my medical course interfere with my education.”

He liked that touch of humor, and the jab at academia would play well with his audience. He addressed the envelope to the Navy Experimental Diving Unit and carried it across the University of Pennsylvania campus. Fair-haired and slender, with intense chestnut eyes and a boyish softness to his jaw, Christian Lambertsen, 25, had been working tirelessly on a single extracurricular project since starting medical school the previous year. While others passed sleepless weeks cramming for exams, Lambertsen had been tinkering with his invention or driving to the Jersey Shore for yet another field test. The project was his sole obsession, so when the navy response came back, he caught the first train to Washington. At his side was a duffel bag filled with an odd jumble of tubes, regulators, and canisters.

In a large hangar-like facility at the Washington Navy Yard, Lambertsen introduced himself to a gallery of spectators. Then he stripped to his underwear and donned his device, which was mounted on a tight-fitting leather harness that resembled a pair of Oktoberfest suspenders. The men in the room had seen other self-contained breathing devices. They were a psychological necessity with the advent of military submarines, whose crews lived in terror of being entombed beneath the sea. In 1910, Englishman Sir Robert Davis created a simplistic breathing-bag apparatus. Oxygen was injected into a rubber lung worn around the neck like a life vest. The lung contained a chemical CO2 scrubber, and the charge of oxygen was rebreathed via a mouthpiece. In a pinch, an escaping sailor could use the device to ascend from a disabled sub, provided the vessel was in shallow-enough water.

In practice, Davis’ device, along with its American counterpart, the Momsen lung, was uncomfortable and worked only for short periods. In 1926, a French navy officer named Yves Le Prieur pioneered a simple open-circuit apparatus that held more promise. Divers using the Le Prieur device breathed oxygen straight from a cylinder and exhaled via a two-way valve into the water. But managing the flow of oxygen was difficult with the primitive regulators of the day, and the meager capacity of available cylinders severely limited the duration a diver could stay under. Jacques Cousteau, often incorrectly credited with inventing the first self-contained breathing apparatus, would improve on Le Prieur’s design later, in the mid-1940s.

But the navy men had never seen anything like Lambertsen’s device, which was as innovative as it was minimalistic, even beautiful. Mounted on the back of the leather harness was a slim 40-liter oxygen tank and regulator flanked by two rubber breathing bags, which inflated in alternating sequence during respiration. A network of hoses connected the rear components to a CO2 scrubber the size of a coffee can near Lambertsen’s sternum, and finally to his mouth and nose via a thick trunk-like hose. He didn’t break a sweat standing before the presenters geared up—the unit weighed only 28 pounds, a far cry from the gargantuan surface-fed hardhat rigs that dominated diving at the time. Given the device’s size, what he was saying sounded impossible: swimming freely, he could stay under for about two hours on a single tank.

After the brief introduction, Lambertsen lowered himself into the pool. Out of his buttoned-up Ivy League attire he was deceptively broad-shouldered, a byproduct of a rough upbringing and many summers spent painting houses on the Jersey Shore with his uncle. After the churn of his entry, he began taking powerful strokes underwater. The onlookers craned to see the wobbly figure gliding along the bottom of the pool. Lambertsen confined the demonstration to about twenty minutes. His device recycled the air he breathed, filtering exhaled CO2 through the chemical canister on his sternum and adding oxygen from the cylinder on his back as necessary. Owing to the innovative closed-circuit design, no bubbles reached the surface.

He was pleased when he climbed out. His machine had worked flawlessly, as expected. But the navy men, if impressed by the ingenuity of it, were underwhelmed by its potential to help win a war. Escaping from a sub took just a few moments, and the Momsen Lung worked well enough for that. The navy’s other diving tasks were best performed with robust hardhat setups fed from the surface, a technology that hadn’t changed much since the 1820s. Any conversation about equipping soldiers with light gear for combat missions was a nonstarter. As far as the navy was concerned, those tactics were for countries that didn’t have the muscle or know-how to go head-to-head in extravagant maritime battles. Lambertsen’s rebreather was a nice toy, a heck of a science experiment, but it wasn’t a tool of war.

Dejected, Lambertsen thanked the men for their time. Then he packed his rig into the duffel and left. He hadn’t noticed the two figures at the back of the small audience, who were doing their damnedest not to attract attention. Jack Taylor, 34, had dark hair, sea-blue eyes, and a movie star’s dashing looks. The other man was a bearded brit named Commander H.G.A. Woolley, 46, a WWI veteran who’d reinvented himself as a Hollywood screenwriter in peacetime but was back in the saddle now that a new war was on. After the demonstration, the pair requested a private meeting with Lambertsen. They had commandeered an indoor pool at a fancy hotel nearby, and they wanted a closer look at the device. Frustrated, the medical student didn’t see the point. This was the navy’s second look—a demonstration some months earlier had sent him back to the drawing board—and it had now passed on the rebreather twice. That’s when Taylor flashed the smile. He had been a Hollywood orthodontist in civilian life. Now that the war was on, he was on his way to becoming one of the most celebrated clandestine operatives of his generation.

They weren’t with the navy.


Taylor and Woolley had spent the past few months trying to piece together the raw ingredients for a first-of-its-kind unit within the OSS, a clandestine intelligence organization of spies and saboteurs. Modeled after the UK’s intelligence apparatus, the agency was created in 1942 to send agents behind enemy lines for espionage and prisoner extraction and to disrupt enemy supplies. It was led by WWI hero and prominent lawyer William “Wild Bill” Donovan, whose ideal candidate was “a Ph.D. who could win a bar fight.” Donovan made sure it was a haven for military misfits, and its ranks grew to include civilian scientists, academics, entertainers, socialites, and professional athletes, whose skills could be weaponized just as easily as a demolition expert’s.

Taylor and Woolley were just Donovan’s sort of oddballs, and exactly the right candidates to create his agency’s newest branch: The Maritime Unit. OSS agents had been parachuting into Germany and occupied France with elaborate covers, but there was a growing need for infiltration and exfiltration by sea. Donovan borrowed Woolley from the British Royal Navy—his reputation for taking risks and experimenting with offbeat tactics preceded him—and placed him in charge of sea-based operations. Taylor was among Woolley’s first recruits, an adrenaline junky who in peacetime had solo-sailed his yacht halfway around the world, flew airplanes to their limit, and survived three days underground after being stuck in an Alaskan goldmine following an avalanche. He had joined the naval reserve in hopes his seamanship would be put to good use, but owing to his medical training he was consigned to drilling cavities for draftees. His new role in the OSS was a much better fit.

To build the Maritime Unit—MU in the acronym obsessed OSS—the pair needed boats, which were in short supply. The navy had helped itself to most of the private yachts of any military value on the eastern seaboard. Having new boats built was out of the question; it would take too long, and the MU had a piddling budget, even by the standards of the resource-constrained OSS. Instead, under the guise of needing some off-hours recreation, Woolley joined the Washington Yacht Club. Wearing his leisure clothes, he made a prompt survey of the unclaimed vessels and found a couple rotting heaps in need of total overhauls. The floating deathtraps seemed to fit the spirit of the new enterprise, and he gleefully relieved the club of its last useable vessels.

Next, Woolley managed to pry enough money from Donovan to rent a remote, overgrown stretch of wild riverbank on the Potomac River south of DC. Throwing up slapdash temporary shelters, which offered little protection against the cold of winter or the incessant mosquitos of summer, they called their rustic proving ground “Area D.” Short on staff and absent military support—the regular military distrusted Donovan and his band of spies—they recruited a couple geezers from a nearby town to guard Area D. The first American maritime spy school was open for business.

The MU had no agents of its own yet, so Donovan charged Woolley with training men from other units. Taylor served as chief instructor and designed a course to teach the first classes of OSS men how to infiltrate enemy shorelines, gather intelligence, and kill using the element of surprise. Students made nighttime raids against gun-toting sentries from the nearby base at Quantico—to the surprise of the sentries, who carried real guns and had never heard of the OSS. They placed charges and blew up dummy boats, learned to use kayaks and rubber rafts to make stealthy approaches, and became experts in maritime sabotage. It was the first time an American military unit had been trained in sea-based special warfare.


But Woolley and Taylor had bigger ambitions. They dissected intelligence reports relating to the Italian Gamma Group swimmers, marveling at the unit’s ingenuity and daring. Woolley inspected the navy’s existing light diving technology, which was unimpressive. He commissioned a new device from an inventor and diving pioneer named Jack Browne, who created a flawed but markedly-improved self-contained rebreather. To put it through its paces, Taylor took Browne to the beaches of Santa Monica for an ocean trial. Taylor had worked as a lifeguard on those same beaches in high school, and the trip had the flavor of a homecoming. Back then, the girls had swooned for the tanned young man perched coolly on the tower. He was pleased to see not much had changed.

Browne’s friend, a former national champion swimmer named Fred Wadley, joined the group, as did a local lifeguard named George Peterson, who served as test subject. They motored out into the blue water beyond the surf, and Peterson eased into the brisk Pacific wearing Browne’s device. Suits to effectively protect swimmers from the cold hadn’t been developed yet, and even rubber swimfins, all the rage on Southern California beaches that year, were something of a novelty. Wadley swam around under the boat for a while and reported back positively. But on his second attempt a faulty regulator released the entire charge of oxygen from the canister, an explosive force that burst the device’s rubber tubes but luckily left Peterson unharmed.

As in previous tests, Browne’s device showed promise but wasn’t anywhere near ready for field use. Back in Maryland, Woolley and Taylor were unsure how to proceed. Taking their idea for a unit of underwater combat swimmers up the chain of command was too risky without proven equipment, and Browne’s device didn’t leave them with much confidence. That’s when word arrived from a contact at the navy that a kid from Pennsylvania was shopping around a gadget he’d hacked together all by himself. Skeptical, they attended the demonstration at NEDU.

They could hardly believe their luck.

Lamb LARU.jpg

The Potomac was murky and polluted, but Taylor pressed on. He had always been able to summon his courage in times of distress. It was in those moments—beating into a gale in his yacht, picking his way out of a cave after an avalanche—that he felt most alive. He would not allow the frigid water to make this an exception.

Wearing Lambertsen’s rebreather, Taylor successfully completed an underwater mile in zero visibility. It was an extraordinary feat, and undoubtedly a world record for distance underwater. Even the Italians approached their targets perched atop their manned torpedoes, only submerging when they were within range.

Lambertsen’s device was the lynchpin, the breakthrough they’d been waiting for to sell the idea of underwater combat swimmers to Donovan, who would eventually have to sell it to the military establishment. Woolley and Taylor started recruiting personnel for the audacious new unit: a swimming coach and naval reservist named Robert Duncan, two navy hardhat divers, John Spence and Norman Wicker, and Fred Wadley, the champion swimmer who helped during the Santa Monica trials. They also recruited Lambertsen as advisor. Still in medical school, he received a special dispensation from Penn thanks to some persuasion from his new colleagues. He would work with the swimmers, take note of necessary improvements, and report back to campus to refine the device—all while ploughing ahead with his medical studies.

One by one the recruits got their chance to try the rebreather, which was rechristened the Lambertsen Amphibious Respiratory Unit, or LARU (the emphasis on roo giving it a francophone grace). Spence, one of the navy divers, would later remember his first trial, which Lambertsen was present for: “To anyone witnessing, you could see the excitement in both of us. My mind raced over the simple marvel of his invention. He created it and I was his test student.” Spence plunged in and was soon doing laps underwater. “It was silent. The only sound was my own breathing. It made me feel kind of like Buck Rogers.” Climbing out of the water during a different test, Spence caught the eye of an onlooker, who called out, “Hey, frogman!”

The term stuck.


To speed up the training, the OSS sent its first five frogmen to the Naval Academy in Annapolis for more tests and a crash course in explosives and close combat—abbreviated spy school. Utilizing the Naval Academy pool, they began to figure out how to maneuver wearing the LARU. Lambertsen made frequent trips to Annapolis to help. Taylor and Woolley figured he’d stand by taking notes, but if there was any question of him staying out of the pool it was put to rest immediately. “He always got in the water with these guys,” says Tom Hawkins, a former Navy SEAL commander and longtime friend of Lambertsen. “He was a chirpy little guy, not the kind to stay on the sidelines.” In conversation, the medical student was reserved, even humble. But he viewed the quest to put his device to use as a question of science. When it came to science, he had both authority and a flair for leadership. He also had the most experience breathing underwater. In the pool, Lambertsen demonstrated the best way to carry loads, such as magnetic limpet mines. He refined the men’s technique in drill after drill. When Spence performed a maneuver unsafely, he stopped the exercise and showed him how to do it right. The frogmen began to view him as a teacher.

To create his first prototype, Lambertsen had used parts from the Ohio Chemical & Manufacturing Company, which built anesthesiology equipment. He had even spent a summer working there to speed up development. Now, working with the company’s president, he commissioned more LARUs built to his specifications. The new models were neutrally buoyant, more robust, and had attachments for compasses and integrated snorkels. “Its classification was at the highest level and on par with the Atomic program,” recalled Spence. He also dreamed up a mechanical underwater communicator that allowed the men to speak to one another on dives. Through the end of 1943, as the swimmers bounced between Annapolis, Area D, and the warmer water off Silver Springs, Florida, they came up with new ideas for equipment that would help with missions. Lambertsen’s relationship with the Ohio Chemical & Manufacturing Company proved essential. The company fashioned waterproof flashlights and specialized containers to transport gear and explosives. The OSS developed waterproof wristwatches with luminous dials, critical for making rendezvous and coordinating attacks. Knives and sheaths were tested, small arms waterproofed, and magnetic mines with reliable timers constructed in packages small enough for a person to carry underwater. The men commissioned inflatable rafts powered by near-silent electric drill motors, which they called flying mattresses, along with inflatable surfboards and swimfins for hands as well as feet.

Taylor would soon be reassigned for a special mission in the Mediterranean, but not before he and Woolley recruited additional swimmers. They targeted every branch of the military, as well as beaches in Southern California, offering alluringly vague pitches to hale young men eager for action. As new recruits arrived, the growing unit was divided into three swimmer groups. Lambertsen, the buttoned-up scientist with no military background, became lead instructor for one of the teams after he graduated from medical school in June 1943. After so much time in classrooms, and with months spent parked in a lab, the fieldwork nurtured something long-dormant—a lust for physical exertion, adventure. He had fashioned himself into a scientist to escape a tough upbringing during the Depression, but beneath his taut exterior lay an untapped store of derring-do. He was settling into a role he was born to play.


















The military was less than enthusiastic. After months of practice, the frogmen seemed no closer to going to war. OSS agents had to be invited by Allied military commanders to participate in missions. The fighting was fierce in the Pacific. During beach invasions, Allied soldiers were getting chewed up by enemy machine guns. Woolley and Taylor discussed the idea of making clandestine landings prior to invasions to destroy enemy defenses, which might save tens of thousands of lives. But General MacArthur, who commanded the southwest Pacific, coldly rebuffed requests to test the theory. Like much of the military establishment, he considered the OSS a mercenary outfit. Even military leaders who saw some value in the agency’s intelligence-gathering capabilities couldn’t get their heads around a unit of underwater combat swimmers.

By 1944, Lambertsen and his men were talking nervously about the possibility of missing out on the war completely. They had relocated to a small private island off Nassau in the Bahamas to continue their training. They dove wrecks offshore, where a four-foot barracuda they called Horace made a game of rushing them menacingly and then stopping a few feet away to churn its jaw. Sharks were a constant worry, especially after a 15-footer started hanging around. One of the repellants the men tested may have been whipped up by Julia McWilliams, who worked in the OSS Emergency Sea Rescue Equipment Section and would later rise to international celebrity under her married name, Julia Child. Lambertsen made a special project of testing and exploring tactical uses for a motorized submersible canoe called the Sleeping Beauty, which the British had designed and sent over for testing. The batteries leaked acid and the vessels were difficult to maneuver, but under Lambertsen’s tutelage the men became proficient in its use.

As summer came, however, the idleness wore on the group. With nothing to lose, Lambertsen and the OSS concocted a plan. 

At 20:15 hours on July 21, 1944, a 50-foot motor launch left dock with four teams of OSS frogmen aboard. They carried full outfits: water-proof wristwatches, flashlights, swimming compasses, sheath knives, M3 submachine guns in waterproof covers, side-arms, and various demolitions designed to function underwater. Assault swimmers on each team wore the latest LARUs.

The boat arrived at the drop-off point at 21:15, and the four color-designated groups disembarked—Red atop paddle-boards, Blue in collapsible kayaks, Black in a large rubber raft, and Orange on flying mattresses. They motored or paddled under a quarter-moon to separate staging areas, where group leaders signaled the all-ready by radio or flashlight. Then the assault swimmers submerged and proceeded to their targets. The American base at Guantanamo Bay was protected from submarine attack by means of underwater listening devices and submarine nets—interlocking metal rings that hung in an unbroken drape across the mouth of the harbor. The swimmers ran quiet and easily cut through or ducked under the nets. When they reached the target ships at anchor, they affixed magnetic mines below the water line.

On ships nearby, representatives from the army, navy, coast guard, and marines, as well as several British military leaders who had flown in for the demonstration, scanned the dark water with binoculars. Fully aware an attack was imminent, they noticed nothing out of the ordinary. Nor did the base’s sophisticated sensing equipment pick up any irregularities. The OSS swimmers were supposed to use dummy charges against the unmanned vessels, so it was a surprise when an explosion ripped through the first boat, brightening the harbor with a brilliant flash. After being snubbed by the navy, Lambertsen enjoyed his revenge—his men had easily infiltrated one of the best-guarded coastal bases in the world, a small demonstration of what the frogmen were capable of. The Italians’ assault on Alexandria a few years earlier looked amateurish in comparison.

News of the successful exercise reached the highest levels of Allied command. In short order, an invitation arrived. Lambertsen and the OSS men had a mission—and it would change the tides of the war in the Pacific.


The doctor was under fire.

Anchored off Burma’s Arakan coast, he watched the night-darkened jungle wink with muzzle flashes. He had only been in country a week, but it didn’t take experience to know which reports belonged to the big 75mm. Those blasts came less frequently, a heart-stopping jolt followed by interminable stretches of calm.

The clandestine operatives he helped ferry behind enemy lines had made it to shore, and the tiny motor launch carrying him and the MU crew was a sitting duck until they returned. As a man of science, he had to appreciate the Japanese gunners—they had methodology. As a man who weighed facts to arrive at probabilistic outcomes, he had to be frightened.

Not that it showed. His foot propped on a gunwale, he looked out from the boat and scrutinized the dark seam of shoreline, the image of a quixotic kid orchestrating a make-believe pirate raid. Only it wasn’t pretend, wasn’t another in the endless series of exercises and drills to test the deadly utility of his inventions or the cunning of his tactics. Lambertsen, whose transformation from bookworm to daring agent and unit leader was complete, had made it to war.

He couldn’t have picked a more menacing battlefield. With support from OSS personnel in other branches of the agency, the frogmen had quickly set up a forward operating camp on the Arakan coast, a desolate, water-logged swamp separated from the rest of Japanese-held Burma by a steep mountain range. "The coast is one of the strangest in the world,” wrote a veteran of the British-led and American-supported effort to drive back the Japanese on India’s doorstep. “It is an almost continuous mangrove swamp broken by thousands of creeks or chaungs.” Massive saltwater crocodiles patrolled the chaungs. Mud devoured everything. Trapped under the slurry, organic matter fermented until gaseous volcanoes erupted in belches of steam and stench.

The war was turning against the Japanese. With their broader hopes dimming, troops under Major Matsu of the 121st Regiment had been holding a portion of the Arakan coast called Ramree Island with a kind of maniacal fervor. They booby-trapped the tidal jungle and concealed themselves in ambush. Hidden coastal batteries waited around each outcropping, and every harbor was mined or littered with debris, making large-scale landings impossible. The Japanese had twice bombed Calcutta from airfields in the Arakan, the bombers racing to deliver their deadly payload before dashing back to the safety of that impregnable curtain of mangroves.

To defeat the Japanese, the Allies had to take the coast, then proceed to Rangoon, Burma’s capital. That was likely to precipitate Japan’s cascading retreat across Southeast Asia, setting up an Allied victory in the Pacific. But it all hinged on a successful invasion, and Major Matsu and his troops were dug in. A superior landing force might be able to overwhelm them, but only at the cost of thousands of lives. It was up to the OSS to gather intelligence, sniff out traps, and find an easier way in.

Lambertsen spotted the rubber boat at last. The landing party had surveilled the lower portion of Ramree Island off the Arakan coast, the location of a large contingent of Major Matsu’s men. They had noted concealed machine gun nests before slipping back to the sea. Lambertsen helped hoist the rubber boat into the motor launch. Then, still under barrage from the coastal battery, they departed, their mission a success.

At the hastily-set-up camp—named Camp Ritchie for an OSS man who had died during a training accident—Lambertsen looked after the men’s health. Officially he was there as a medical officer and not permitted to go on missions, though no one stopped him. During sweltering tropical days he kept the men sharp and in shape by leading them through exercises—jumping jacks, lunges, jogging. In the dead of night he accompanied them on missions. The OSS skulked up the muddy Kaladan River to interrogate natives and recruit locals in intelligence-gathering against the Japanese. Sometimes the surrounding jungle fell silent, and then the river exploded with small arms fire. Unable to see the source of the shots, the OSS men submerged in the muddy water, their only cover, and made hasty retreats.

Nighttime landings on Ramree Island allowed the men to make careful observations of enemy artillery and troop distribution. During one landing, a Japanese soldier on patrol surprised the shore party in a dense thicket of mangrove jungle. The OSS men made quick work of the sentry with a burst of machine gun fire, but the skirmish alerted enemy soldiers at a Japanese headquarters nearby. Sprinting back to the safety of the sea, the OSS men disappeared as quietly as they had come, the shell casings and the dead body the only traces left behind.

For another mission, code-named Cleveland, Lambertsen and the swimmers proceeded on a high-speed motor-torpedo boat toward Sagu Island, deemed a possible landing site for the anticipated invasion. The swimming parties wore waterproof .45 caliber pistols and sheath knives, red-filter flashlights, wrist compasses, and sneakers. Their primary objective was to make an underwater survey of the area, and they carried sounding lines to determine depth and feel for wreckage and debris, as well wrist tablets and wax pencils to take notes. A landing party reached shore in kayaks and rubber boats. Surveilling the island, the men came across an enemy agent. Taking a chance that he was alone, they sprang out from a concealed position and tackled him, covering his mouth so he wouldn’t make a sound. Binding his hands, they marched the man at gunpoint to the rubber boat, and then hurried back to their rendezvous. The captive was interrogated, yielding valuable intelligence.

After a month swimming up rivers, landing on hostile beaches in the dead of night, and staking out enemy positions, the so-called Arakan Field Unit—AFU, or “All Fucked Up,” in the parlance of the OSS—had made small incursions into most of the coastline, gleaning detailed information about defensive positions and troop strength. In late January of 1945, the Allied invasion began with an assault on a harbor on the north end of Ramree Island. The British Royal Navy sent a hail of preemptive fire from ships anchored offshore, including the HMS Queen Elizabeth, which had been repaired and relaunched after her run-in four years earlier with the Italian frogmen. Thanks to the excellent reconnaissance, the invading force knew the terrain and was prepared for every defensive battery and submerged threat. RAF aircraft spotted the assault, radioing back hits and misses and strafing concealed enemy positions. The strike was surgical. The Japanese didn’t know what hit them.

Hitchhiking aboard British minesweepers at the front of the invasion, delighting in a job well done, the OSS men were among the first groups to land. Shortly after arriving, four divers donned LARUs to survey the harbor for mines and underwater obstructions. Unlike the bloody landings on the beaches of Tarawa, Guadalcanal, and Iwo Jima, the invasion of the Arakan coast resulted in few Allied casualties.

By early February, the invading force outflanked the 900 remaining Japanese. Instead of surrendering, Major Matsu’s soldiers attempted to fall back into the mangrove swamps. “Without food or water, prey to the flies, the leeches and the crocodiles, with their feet swollen to lumps of flesh that showed no toes from stepping on mangrove shoots, they stumbled on,” wrote Lt. Commander Bruce Wright, a Canadian Naval Officer who took part in the invasion. Hell bent on avoiding capture, few Japanese survived.

Lambertsen was a hero. Public acknowledgement of his contributions was impossible at the time—the activities of the frogmen were highly classified—but he would eventually receive the OSS Legion of Merit and the US Department of Defense Distinguished Public Service Medal. Following the war, the OSS was hastily disbanded, the technology it developed warehoused or discarded. Lambertsen returned to medicine, but he also tirelessly lobbied to have the LARU rebreather declassified. In 1948, after years of knocking on the navy’s door, he was finally invited to demonstrate the LARU in open water. During that training, he became the first person to exit a submarine wearing an oxygen rebreather. The demonstrations prompted the Navy to rethink its stance on underwater combat swimmers, and teams using Lambertsen’s techniques and technology deployed in the Korean War. The first official SEAL teams were established in 1962.

Outside the tight-lipped special warfare community, Lambertsen, who coined the acronym SCUBA and went on to do work for NASA and other agencies, rarely spoke about his WWII days. “He took care of his men and he never wanted the spotlight,” says Hawkins. He died in 2011 at the age of 93, not long after the OSS files detailing the adventures of the frogmen were declassified.

The navy officially recognizes him as the Father of US Combat Swimming. Today the SEALs are the spear tip of America’s military might.