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Dr. Christian Lambertsen

The Father of American Combat Swimming

During World War II, one of the greatest of the many great challenges facing the Allies was the means of conducting covert underwater reconnaissance and sabotage missions in littoral waters. The Italian Navy, with its special operations 10th Light Flotilla, had spectacularly proved the feasibility of such missions with its manned torpedo attack against the Royal Navy in Alexandria harbor on Dec. 19, 1944, which sank two battleships and a tanker and severely damaged a destroyer. As with all the other new aspects of warfare in that conflict, Allied military leaders knew this was a field of operations in which development of doctrine, design, and construction of equipment, training – in other words, everything – would be a work in progress conducted in the pressure cooker of a shooting war. One person who was not just integral, but invaluable, to the success of Allied covert underwater combat swimming operations was Dr. Christian James Lambertsen.

Lambertsen’s contributions – and here must be stressed the plural – began in World War II and continued for almost four decades. His comprehensive background and experience as a doctor, inventor, and diver made him a unique all-in-one asset; literally the right man in the right place at the right time. His education and research in the new fields of undersea, diving, and hyperbaric (medical use of oxygen at levels greater than atmospheric pressure) medicine coupled with his own diving experience gave him vast empirical and practical knowledge of the physiological effects and dangers of such conditions as oxygen toxicity, hypoxia, prolonged activity underwater at depth, and other dangers. This knowledge, combined with his ability as an inventor, crucially facilitated the development of one of the most innovative self-contained rebreather units ever made, the Lambertsen Amphibious Respiratory Unit. That alone would have secured Lambertsen’s reputation in special operations. But, Lambertsen’s contribution didn’t stop there. He also developed and refined training doctrine, instructed and mentored combat swimmers, and worked on testing and evaluating a one-man submersible canoe designed for special operations, code-named “Sleeping Beauty.” In his long and storied, though covert, career, it’s not an exaggeration to say that Lambertsen “did everything.” It was no surprise, then, that the U.S. Navy SEALs honored him in 2000 with the accolade “Father of U.S. Combat Swimming.”

Lambertsen was born in Westfield, N.J., on May 15, 1917, and grew up in neighboring Scotch Plains. He spent his summers vacationing on the Jersey Shore, and when he was old enough, earned money by helping paint houses for one of his uncles. While in high school, he decided on a medical career. After graduation, he enrolled at a local junior college. Upon receiving his associate degree, he secured a two-year scholarship that allowed him to attend Rutgers University, where he graduated with a bachelor’s of science degree. In September 1939, the same month World War II erupted in Europe, Lambertsen entered the University of Pennsylvania School of Medicine in Philadelphia.

At medical school, he studied respiratory physiology, of which little was known at the time. He conducted numerous experiments studying the effects of hypocapnia (a state of reduced carbon dioxide in the blood as a result of hyperventilation), hypoxia (oxygen deprivation), hypercapnia (an excess of carbon dioxide in the body), and other respiratory conditions. During the summer breaks, he returned to the Jersey Shore, once again to earn money working for his uncle. During the weekends, he put to use the lessons he learned in his medical school research to conduct informal “field experiments.” Together with the help of a couple of cousins, he performed underwater experiments. The first began with the use of a homemade rebreathing rig consisting of a mouthpiece and bag connected to a long hose that was attached to a bicycle pump. The cousins would operate the pump, providing fresh air to Lambertsen as he swam underwater. This awkward (and no doubt for the cousins, tiring) system was soon replaced by a cylinder of compressed oxygen. This system proved unsatisfactory due to the accumulation of carbon dioxide in his air bag. Shortly thereafter Lambertsen learned of a new type of anesthesia equipment that used a carbon dioxide absorbent to solve the accumulation problem. Encouraged, Lambertsen fashioned a small carbon dioxide scrubber that fit between his mouth and the breathing bag. Though the arrangement was crude, it worked.

OSS Maritime Unit

OSS Maritime Unit diver employing the “Lambertsen Lung,” an early pure oxygen rebreathing apparatus. Photo courtesy of Tom Hawkins

Lambertsen had kept Dr. Henry Bazett, his physiology professor, informed of his work. Bazett responded with enthusiasm and contacted Cleveland-based Ohio Chemical and Manufacturing Company, a maker of anesthesia equipment, informing them of his student’s work and requesting additional parts. Ohio Chemical instead offered Lambertsen a job during the summer of 1940 at the then-princely salary of $30 per week. After a meeting with the company’s president, J.G. Sholes, it was mutually decided that Lambertsen’s task during the summer would be to move to Minneapolis, Minn., where the company had a plant manufacturing anesthesia equipment, and there work on an underwater breathing device that could be used in lifesaving.

The result was a 12-pound, semi-closed pendulum rebreather equipped with a 40-liter oxygen bottle and a carbon dioxide scrubber. Lambertsen conducted underwater experiments at Lake Nokomis, near Minneapolis, and later at Lake Erie, near the company’s main office. Lambertsen performed the underwater tests himself and discovered that he could do about a half-hour of light work down to a depth of 60 feet. The success of these tests caused Lambertsen to suggest to Sholes that the apparatus might be useful for miners trapped in passages containing hazardous atmospheres. Excited by the idea, Sholes ordered a gas-tight chamber constructed on a loading dock where they could conduct a hazardous atmosphere demonstration. Inside the large airtight wood and Plexiglas® structure were a canary, a dog, and Lambertsen, who was wearing his rebreather. The chamber was flushed with carbon dioxide to remove all oxygen, and then filled with cyclopropane, a highly flammable anesthetic gas, to simulate underwater conditions. The audience in attendance included newspaper and newsreel reporters, police and fire department units, as well as company officials.

After a few minutes, the canary fell unconscious. Not long after that, the dog dropped to the floor, also unconscious. It was about 20 minutes into the demonstration that Lambertsen leaned down to check on the dog. When he did so, he too fell to the floor unconscious. The firefighters immediately used their axes to break open the chamber and rescue the occupants. An examination of Lambertsen’s rebreather revealed that the cyclopropane had slowly penetrated the breathing bag’s latex shell.

News of the demonstration was circulated throughout the nation because at that time, use of an artificial breathing device for 20 minutes “underwater” was an extraordinary achievement. By the time Lambertsen returned to Philadelphia to continue his studies, he was a celebrity. Bazett was thrilled, writing to the Journal of the American Medical Association: “The equipment was successful because it was designed by a man who studied the physiological principles carefully and is capable not only of testing it himself but training the users. It could not have been developed by a physiologist unfamiliar with the practical side nor by a swimmer without physiological training.” More importantly, Bazett, a British citizen, felt Lambertsen’s device had military applications. He sent a letter to the British Admiralty, writing, “The apparatus has advantages in lightness and freedom of movement in the water making it adaptable either for use of underwater troops of the trouble-making type or for night-raiding enemy defenses.” Bazett also arranged for a demonstration for the U.S. Navy conducted in Washington, D.C., for the Navy Experimental Diving Unit (NEDU) in January 1941. Though the demonstration was successful, the Navy passed on his device. Even so, Lambertsen received encouragement from Lt. Al Behnke, a junior medical officer who witnessed the demonstration. Crucially for the future of special operations frogmen, Lambertsen came away with a firm belief that the future for his apparatus lay with the military – and that he would have to do a major redesign.

The result of his new efforts was the Lambertsen Amphibious Respiratory Unit II (LARU II). It featured a more robust design, and a new air recirculating arrangement that made carbon dioxide removal more efficient.


Christian Lambertsen models his invention, the Lambertsen Amphibious Respiratory Unit (LARU) Mark I, in 1940. It was the first underwater rebreather device allowing a diver to move about without producing breathing bubbles that could be seen on the water’s surface. USPTO / NSW Publications, LLC

A second NEDU demonstration was scheduled for April 1942, and this time, in addition to Navy personnel, representatives from the British Special Operations Executive (SOE) and U.S. Office of Strategic Services (OSS) were on hand. Both agencies had been looking for an underwater breathing apparatus that would enable frogmen to conduct long-term, covert underwater missions in littoral waters, and the men saw in Lambertsen’s unit the answer to their needs. Encouraged by what they saw, the OSS arranged to have Lambertsen work for them during his senior year. Upon his graduation from medical school in June 1943, Lambertsen tried to enlist in the Navy but was rejected because he suffered from hay fever. The OSS, however, was willing to look past his allergy affliction. Lambertsen was recruited by the OSS, commissioned a first lieutenant in the Army Medical Corps, and assigned to its new OSS Maritime Unit (OSSMU), where he would both continue work on his underwater breathing apparatus and train swimmers in its use.

The aspect that made the Lambertsen Unit particularly attractive to the OSS and SOE was its rebreather capability. The carbon dioxide scrubber, consisting of soda lime, not only allowed the frogman to reuse the oxygen in the self-contained system, but did not leave any tell-tale exhaust air bubbles like conventional scuba equipment.

One member of the OSSMU was the legendary Jack Taylor. A naval reservist, then-Lt. Taylor was one of the first three officers posted to the OSSMU when it was formed in early 1942. He began training in “Area D,” an OSS training facility on the shore of the Potomac River directly across the river from the Marine Corps base at Quantico, Va. In addition to training, the men tested a variety of equipment, including the new Lambertsen Amphibious Respiratory Unit III (LARU III). Two underwater swimming groups, called “L-Units,” were subsequently formed. During one test of the LARU III during this period, Taylor remained underwater for more than 48 minutes and swam more than one mile, at the time an extraordinary achievement. Taylor would subsequently go on to conduct missions in the Mediterranean and Middle Eastern theater of operations. Captured while conducting Operation Dupont – a mission in Austria to try and establish resistance cells – at the end of November 1944, he was taken to the Mauthausen concentration camp. He was liberated by Soviet troops on May 5, 1945. Taylor would receive the Navy Cross for his participation in Operation Dupont. He was promoted to the rank of lieutenant commander and was a witness at the Nuremburg war crimes trials before being discharged.

By May 1944, the OSSMU had organized three Operational Swimmer Groups (OSG), totaling 226 personnel. Declassified records revealed that it was a joint service effort, with men from the Army, Navy, Marine Corps, and Coast Guard. It even included four civilians in its ranks. It was now time for a full-scale, dress-rehearsal exercise to see whether or not all the planning and training really worked.

Code-named Operation Cincinnati, it was the first exercise of its kind designed to test shore defenses protecting military facilities – in this case the U.S. Navy’s harbor defenses in Guantanamo Bay, Cuba. As such, it pre-dated by almost 40 years the Red Cell teams of SEAL Team Six formed in 1984 for the same purpose.

As detailed in Operational Order #5, the mission of Operation Cincinnati was for four teams of nine men each (designated Red Group, Blue Group, Black Group, and Orange Group) to enter the harbor and “destroy 4 enemy ships between the hours of 2000 and 2400 on 21 July 1944.” In addition, the groups were ordered to “preserve the highest degree of secrecy and security in connection with all phases of this attack and in particular concerning the method of attack.”

The exercise commenced at 2015 (8:15 p.m.) when the four groups boarded their 50-foot mother ship laden with their equipment, which included Lambertsen Units for each man. The Lambetsen Unit was not the only piece of equipment being tested in the exercise. Each group was assigned different transportation equipment and vessels, the goal being to determine the suitability of each. Group Red had rubber paddleboards, Group Blue two-man kayaks, Group Black a seven-man rubber boat, and Group Orange a “flying mattress.”

UDT Small Submersible

A small submersible and its pilot make the first successful rendezvous and docking with a submerged submarine on the USS Quillback’s foredeck in 1948. Divers from UDT-2 and UDT-4 employed Lambertsen rebreathers. Photo courtesy of Tom Hawkins

Operation Cincinnati was a success. All the teams performed their assigned tasks without detection. In his evaluation, OSS operative Kermit Roosevelt wrote, “In these tests, the lengthy training showed commendable results, because the swimmers were able to circumvent the net defenses in each instance. An additional point of value was proof that the Navy sound detection gear did not reveal the presence of underwater swimmers.”

Field deployment began in January 1944, with units sent to Europe and the China, Burma, India (CBI) theater. From bases in Italy, operations in the Mediterranean were conducted in the Adriatic and Aegean seas and ran the gamut. They included maritime sabotage, sneak attacks, ferrying weapons, agents, and supplies to resistance units and evacuating downed fliers and refugees from occupied territories. Teams based in England conducted similar operations in Scandinavia.

In the CBI, teams were stationed in Ceylon (present-day Sri Lanka), Burma, and India. Most of the operations involved intelligence gathering. One particularly harrowing mission in the CBI was Operation Cleveland, conducted on Jan. 25, 1945. In addition to obtaining intelligence of the target area, including a survey of the coastline, terrain, and strength and status of enemy forces in the area, it also included the capture of a native, or an enemy soldier, for purposes of interrogation. Needless to say, the most difficult aspect of the operation was the live capture and exfiltration of an enemy soldier. The team accomplished every aspect of the difficult mission, including the capture of an enemy soldier.

Meanwhile, the SOE had developed the Sleeping Beauty, an underwater one-man craft similar to the one-man submarines used by Italy’s 10th Light Flotilla. Lambertsen’s involvement with the Sleeping Beauty started in January 1944, when an L-Unit returned from England after having trained with SOE teams for missions in support of D-Day, which were canceled because mission requirements proved to be beyond the teams’ capabilities. The teams brought with them a Sleeping Beauty and Lambertsen, by now a captain, immediately developed doctrine and procedures for its use. His work in this area continued after he was stationed in Ceylon and given two Sleeping Beauties to work with. His work with the Sleeping Beauty, eventually became the foundation for the swimmer delivery vehicle concept.

Lambertsen was discharged from the Army in 1946 with the rank of major. Though a civilian and working at the University of Pennsylvania Medical School, Lambertsen’s role with special operations was not over. By now, the OSS had been disbanded and it looked like the Navy’s special operations Underwater Demolition Team (UDT) program would soon follow. Lt. Cmdr. Francis Douglas “Red” Fane was in charge of two reduced-strength UDT teams stationed in Little Creek, Va. Wanting to save the force from demobilization, he contacted a number of scientists and experts in the field. A key member of this group was Lambertsen. Lambertsen was instrumental in developing new and innovative doctrine and training for UDT swimmers that increased their mission capabilities and helped save the unit from administrative extinction.

Lambertsen would go on to have a distinguished career in medicine. In 1968, he founded the Institute for Environmental Medicine at the University of Pennsylvania. He also received numerous military and civilian decorations and honors, among them the Presidential Unit Citation for service in Burma with OSS Unit 101, the Legion of Merit, and Honorary Lifetime Membership in the UDT-SEAL Association and the OSS Society’s Distinguished Service Award.


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    Leslie H Fenton MD , PhD, FACP ( CDR, USNR, Ret)

    Excellent summary of many of Dr. Lambertsen’s contributions as the “Father of American Combat Swimming”.

    The full extent and timing of Dr Lambertsen’s contributions continued through direct involvement and leadership in solving operational limiting issues that had essentially stopped Dry Deck Shelter / SEAL Deivery Vehicle (SDV) operations in 1986-87. As a member of The National Research Counsil Subcommitee on Toxopharmacology and working directly with operational Naval Special Warfare Units, Dr. Lambertsen provided leadership, technical and operational expertiise that resulted in the successful delivery of safe diver quality from host submaines for Dry Deck Shelter and SDV operations. Dr . Lambertsen continued direct support of Naval Special Operations through the 1990s and to Naval Special Warfare Development Group from 2001 – 2006.