Underwater Demolition Team
|Underwater Demolition Teams|
Patch of the Underwater Demolition Teams.
|Active||15 August 1942 – 1 January 1983|
|Branch||United States Navy|
|Garrison/HQ||Fort Pierce, Florida, U.S.
Maui, Hawaii, U.S.
|Nickname(s)||UDT, The Frogmen|
Battle of Iwo Jima
Battle of Okinawa
Battle of Peleliu
Battle of Saipan
Battle of Tinian
Battle of Guam
Battle of Leyte
Invasion of Lingayen Gulf
The Underwater Demolition Teams (UDT) were an elite special-purpose force established by the United States Navy during World War II. They also served during the Korean War and the Vietnam War. Their primary function was to reconnoiter and destroy enemy defensive obstacles on beaches prior to amphibious landings. They also were the frogmen who retrieved astronauts after splashdown in the Mercury through Apollo manned space flight programs.
The UDTs reconnoitered beaches and the waters just offshore, locating reefs, rocks, and shoals that would interfere with landing craft. They also used explosives to demolish underwater obstacles planted by the enemy. As the U.S. Navy's elite combat swimmers, they were employed to breach the cables and nets protecting enemy harbors, plant limpet mines on enemy ships, and locate and mark mines for clearing by minesweepers. They also conducted river surveys and foreign military training.
The UDTs pioneered combat swimming, closed-circuit diving, underwater demolitions, and midget submarine (dry and wet submersible) operations. They were the precursor to the present-day United States Navy SEALs.
The United States Navy studied the problems encountered by the disastrous Allied amphibious landings during the Gallipoli Campaign of World War I. This contributed to the development and experimentation of new landing techniques in the mid-1930s. In August 1941, landing trials were performed and one hazardous operation led Second Lieutenant Lloyd E. Peddicord to be assigned the task of analyzing the need for a human intelligence (HUMINT) capability.
When the U.S. entered World War II, the Navy realized that in order to strike at the Axis powers the U.S. forces would need to perform a large number of amphibious attacks. The Navy decided that men would have to go in to reconnoiter the landing beaches, locate obstacles and defenses, as well as guide the landing forces ashore. In August 1942, Peddicord set up a recon school for his new unit, Navy Scouts and Raiders, at the amphibious training base at Little Creek, Virginia.
In 1942, the Army and Navy jointly established the Amphibious Scout and Raider School at Fort Pierce, Florida. Here Lieutenant Commander Phil H. Bucklew, the "Father of Naval Special Warfare", helped organize and train what became the Navy's 'first group' to specialize in amphibious raids and tactics.
Pressure to further implement human intelligence gathering prior to landings heightened after Naval amphibious landing craft were damaged by coral reefs during the Battle of Tarawa in November 1943. Aerial reconnaissance incorrectly showed the reefs were submerged deep enough to allow the landing craft to float over. Sailors and Marines were forced to abandon their craft in chest deep water a thousand yards from shore, helping Japanese gunners inflict heavy U.S. casualties. After that experience, Admiral Kelley Turner, Commander of the 5th Amphibious Force, directed that 30 officers and 150 enlisted men be moved to Waimanalo ATB (on the island of Oahu) to form the nucleus of a reconnaissance and demolition training program. It is here that the UDTs of the Pacific were born.
A memorial to the founding of the UDT has been built at Bellows Air Force Station near the original Amphibious Training Base (ATB) Waimanalo.
It became apparent that in addition to the Scouts and Raiders, a group of specialists to destroy obstacles was required. In late 1942, a group of Navy salvage personnel received a one-week concentrated course on demolitions, explosive cable cutting and commando raiding techniques. The Navy Scouts and Raiders unit was first employed in Operation Torch, the invasion of North Africa in November 1942. During Torch, this unit cut the cable and net barrier across a river in North Africa, allowing Rangers to land upstream and capture an airfield.
The NCDU teams, each consisting of one officer and five raiders were to clear the beaches of obstacles for the invasion force with the team coming ashore in an LCRS inflatable boat with their explosives.
In 1943, the Navy decided to create a large dedicated force for such tasks: the Naval Combat Demolition Units (NCDU). On May 7, Admiral King, the CNO, picked Lieutenant Commander Draper L. Kauffman USNR to lead the training. The first six classes graduated from "Area E" at NTC Camp Peary. From there it was moved to Fort Pierce.
The expansion of the force meant recruitment beyond the pool of experienced combat swimmers. Most of Kauffman's volunteers came from the Seabees (the Navy's Construction Battalions), the U.S. Marines, and U.S. Army combat engineers. Training commenced with one grueling week designed to "separate the men from the boys". Some said that "the men had sense enough to quit, and left the boys." It was and is still considered the first "Hell Week."
Kauffman's experience was at disarming explosives; now he and his teams were learning to use them offensively. One innovation was to use 2.5-pound (1.1 kg) packs of tetryl placed into rubber tubes, thus making 20-pound (9.1 kg) lengths of explosive tubing that could be twisted around obstacles for demolition.
At the beginning of November 1943, six men from Kauffman's Naval Combat Demolition Unit Eleven (NCDU-11) were sent to England to start preparations for the Normandy invasion. Later NCDU-11 was enlarged into 13-man assault teams. Weeks before the invasion, all available Underwater Demolition men were sent from Fort Pierce to England. By June 1944, 34 NCDU teams were deployed in England.
The Germans had constructed intricate defenses on the French line. These included steel posts driven into the sand and topped with explosives. Large 3-ton steel barricades called Belgian Gates were placed well into the surf zone. Reinforced mortar and machine gun nests were dotted along the beaches.
The Scouts and Raiders spent weeks gathering information during nightly surveillance missions up and down the French coast. Replicas of the Belgian Gates were constructed on the south coast of England for the NCDUs to practice demolitions on. It was possible to blow a gate to pieces, but that only created a mass of tangled debris spread along the beaches, thereby creating more of an obstacle. The NCDU found that the best method was to sever the key corner joints in a gate, so that it fell down flat.
According to the Allied attack plans, infantry supported by naval gunfire would make the initial landings, followed by tanks and troop carriers to clear any remaining German bunkers and snipers. The NCDU teams (designated Demolitions Gap-Assault teams) would come in with the second wave and work at low tide to clear the obstacles. Their mission was to open sixteen 50-foot (15 m) wide corridors for the landing at each of the U.S. landing zones (Omaha Beach and Utah Beach).
Unfortunately, the plans could not be executed as laid out. The preparatory air and naval bombardment was ineffective, leaving many German guns in position to fire on the attackers. Also, tidal conditions caused many of the NCDU teams to land prematurely - in some cases ahead of the first wave. Despite heavy German fire and resulting casualties, the NCDU men planted charges and demolished many obstacles. As the infantry came ashore, some soldiers took cover on the seaward sides of obstacles that had demolition charges on them. They quickly moved onto the beach.
The greatest difficulty was at Omaha Beach. By nightfall only thirteen of the planned sixteen gaps were open, and of the 175 NCDU men who went ashore there, 31 were killed and 60 were wounded.
The attack on Utah Beach was much more successful. There, only four were killed and eleven wounded, when an artillery shell hit a team working to clear the beach.
NCDUs also served in the Pacific theater. NCDUs 2 and 3 were transferred there, and formed the nucleus of a group of six NCDUs.
World War II
The first UDTs to use that designation were formed in the Pacific Theater.
The invasion of Tarawa in November 1943 nearly met disaster due to obstacles in the surf. Tarawa lies in eastern Micronesia. The islands in this region have unpredictable tides and are surrounded by shallow reefs that block even shallow-draft craft, except at a few narrow channels or at high tide. At Tarawa, an unusual Neap tide (a condition that results from the tide not rising or lowering as usual) occurred, leaving insufficient clearance for the Higgins boats (LCVPs) to get over the reef. The Amtracs carrying the first wave crossed the reef successfully. But the LCVPs carrying the second wave ran aground on the reef. The Marines had to unload and wade to shore. Many drowned or were killed before making the beach. The first wave, fighting without reinforcements from the second wave, took heavy losses on the beach. It was a painful lesson that the Navy would not permit to be repeated.
Admiral Kelly Turner, the Navy's top amphibious expert, ordered the formation of nine Underwater Demolition Teams. As with the NCDUs in Europe, the personnel for these teams were mostly Seabees. These volunteers were organized into Combat Swimmer Reconnaissance Units, becoming the Navy UDTs.
UDT training was at Waimānalo, Hawai'i on Oahu under the aegis of V (Fifth) Amphibious Force. Among both instructors and trainees, there were graduates of the Fort Pierce schools (Scouts and Raiders, and NCDU men),Seabees, Marines, and Army soldiers. Under the direction of Marine Amphibious Reconnaissance Company, they hastily trained for the attack on Kwajalein on 31 January 1944.
The training made use of inflatable boats and included surprisingly little swimming. The men were expected to paddle in, and work in shallow water, leaving the deep-water demolitions to the Army. Marine Reconnaissance units would conduct the hydrography from shallow water to inland while the accompanying UDT would conduct the demolition and hydrography from near-deep water to the shallows.
The UDTs were organized with approximately sixteen officers and eighty men each. One Marine and one Army officer were liaisons within each team. It became apparent that a UDT assigned to the same beach as a Marine unit should be embarked in the same high speed transport (APD).
At that time the men in the teams wore Navy fatigues with boots and helmets. They were lifelined to their boats and stayed out of the water as much as possible. The next objective was Kwajalein and the original plan called for night reconnaissance. However, Admiral Turner did not want a repeat of Tarawa and wanted to know about the coral and any obstacles the Japanese may have emplaced. To find this out UDT 1 was ordered to do two daylight recons. In keeping with the Seabee traditions of: 1.doing whatever it takes to accomplish the job and 2. not always following military rules to get it done, UDT 1 did both. The missions were to follow the standard procedure with each two-man team getting close to the beach in a rubber boat, wearing full fatigues, boots, life jackets, and metal helmets, and then make their observations. But, team 1 found that the coral reef kept their craft too far from shore to be certain of the beach conditions. Seabees Ensign Lewis F. Luehrs CEC and Chief Bill Acheson had anticipated that they would not be able to carry out the assignment following the Fort Pierce model and had worn swim trunks beneath their fatigues. Stripping down, they swam 45 minutes undetected across the reef. When they returned with sketches of gun emplacements and other vital intelligence, they were taken directly to Admiral Turners flagship, still in their trunks, to report. Afterwards Admiral Turner realized that the only way to get this kind of information was from individual swimmers and he relayed those thoughts to Admiral Nimitz. The planning and decisions of those two Seabees along with Admiral Turner's needs made Kwajalein a transition point in UDT history changing both the mission model and training regimen. Seabees made up the majority of the men in teams 1-9 and 13. The Officers of those teams were primarily CEC (Seabees). After Kwajalein, the UDTs created the Naval Combat Demolition Training and Experimental Base at Kihei, next to the Amphibious Base at Kamaole on Maui expanding upon what had been learned from UDT 1. Operations began in February 1944. Most of the procedures from Fort Pierce were changed. They were replaced with an the emphasis on developing strong swimmers, daylight reconnaissance, training without lifelines. The uniform of the day changed to face-masks, swim trunks, fins and a K-bar creating the image of the UDTs as the "Naked Warriors". Eventually, 34 UDTs were established and were deployed in every major amphibious landing in the Pacific.
In April, Draper Kauffman was transferred from Fort Pierce to command UDT 5 and serve as senior staff officer, Underwater Demolition Teams, Amphibious Forces, and Underwater Demolition Training Officer, Amphibious Training Command.
UDT 10 was directly under the OSS. It had a secret base on Santa Catalina Island, California before the Maui base was operational. When the team was being formed it was joined by 5 officers and 21 men that had been trained by the OSS. They were lead by a Lt A.O.Chote Jr. who was made 10's commanding officer.
UDT 14 was the first all Navy team (fleet).
The landings continued. Kauffman led UDT 5 in daylight recon of the defenses of Saipan and in a night recon of the defenses of Tinian. UDT 15 reconnoitered beaches at Luzon in the Philippines. UDT 15 also reconnoitered Iwo Jima, two days ahead of the invasion along wirg UDTs 12, 13, and 14. The UDT suffered only one man wounded in action. However, the next day a Japanese plane bombed their APD, USS Blessman. 15 men of UDT 15 were killed, and 23 were injured. This was the single largest loss of life suffered by the UDTs in the Pacific theater. At Iwo Jima the teams not only did reconnaissance but on D-plus 2 were called upon to help clear the beaches of broached or damaged landing craft. The waters edge had become so clogged with debris that there was no place for landing craft to get ashore.
UDTs also served at Eniwetok, Guam, Angaur, Ulithi, Peleliu, Leyte, Lingayen Gulf, Zambales, Labuan, and Brunei Bay. The last UDT demolition operation of the war was on 4 July 1945 at Balikpapan, Borneo.
The largest UDT operation was in support of the invasion of Okinawa, in March 1945. Veteran UDTs 7, 12, 13, and 14, and newly trained UDTs 11, 16, 17, and 18 participated: nearly 1,000 men. Up to that time, all UDT missions in the Pacific had been in warm tropical waters. Now the forces moved north toward Japan where the waters around Okinawa were cool enough that long immersion could cause hypothermia and severe cramps. With no thermal protection at that time, the UDTs were at risk to this during the operations around of Okinawa.
Operations included both real reconnaissance and demolition at the actual invasion site, and feints to create the illusion of landings in other locations. Pointed poles set into the coral reef of the beach protected the landing beaches on Okinawa. UDTs 11 and 16 were sent in to blast the poles. After all the charges were set, the men swam clear. The explosions took out all of UDT 11's targets and half of UDT 16's. UDT 16 aborted the operation due to the death of one of their men; hence, their mission was considered a failure and a disgrace. UDT 11 was sent back the following day to finish the job, and then remained to guide the forces to the beach.
The UDTs continued to prepare for the invasion of Japan until Japan surrendered in August 1945, and their role in the Pacific came to an end. Within months of the war's end, the UDT teams were dispersed. This ended a trying but evolutionary time in the history of Naval Special Warfare.
After World War II
Two half-strength UDTs were retained, one on each coast. Though no combat operations seemed likely, the UDTs continued to research new techniques for underwater and shallow-water operations.
One area was the use of SCUBA equipment.
Dr. Chris Lambertsen had developed the Lambertsen Amphibious Respiratory Unit (LARU), an oxygen rebreather, which was used by the Maritime Unit of the OSS. In October 1943, he demonstrated it to LCDR Kauffman, but was told there was no place in current UDT operations for this radically new device.
However, Dr. Lambertsen and the OSS continued to work on closed-circuit oxygen diving and combat swimming. When the OSS was dissolved in 1945, Lambertsen retained the LARU inventory. He later demonstrated the LARU to Army Engineers, the Coast Guard, and the UDTs. In 1947, he demonstrated the LARU to LCDR Francis "Doug" Fane, then a senior UDT commander.
LCDR Fane was enthusiastic for new diving techniques. He pushed for the adoption of rebreathers and SCUBA gear for future operations. But the Navy Experimental Diving Unit and the Navy Dive School (which used the old "hard-hat" diving apparatus) declared it was too dangerous. Nonetheless, Fane invited Dr. Lambertsen to NAB Little Creek, Virginia in January 1948 to demonstrate and train UDT personnel in SCUBA operations. This was the first-ever SCUBA training for Navy divers. Following this training, Fane and Lambertsen demonstrated new UDT capabilities with a successful lock-out and re-entry from USS Grouper (SS-214), an underway submarine, to show the Navy's need for this capability. LCDR Fane then started the classified “Submersible Operations” or SUBOPS platoon with men drawn from UDT 2 and 4 under the direction of LTJG Bruce Dunning.
LCDR Fane also brought the conventional "Aqua-lung" open-circuit SCUBA system into use by the UDTs. Open-circuit SCUBA is less useful to combat divers, as the exhausted air produces a tell-tale trail of bubbles. However, in the early 1950s, the UDTs decided they preferred open-circuit SCUBA, and converted entirely to it. (The remaining stock of LARUs was supposedly destroyed in a beach-party bonfire.) Later on, the UDT reverted to closed-circuit SCUBA, using improved rebreathers developed by Lambertsen.
The UDT also began developing weapons skills and procedures for commando operations on land in coastal regions. The UDT started experiments with insertion/extraction by helicopter, jumping from a moving helicopter into the water or rappelling like mountain climbers to the ground. Experimentation developed a system for emergency extraction by plane called "Skyhook." Skyhook utilized a large helium balloon and cable rig with harness. A special grabbing device on the nose of a C-130 enabled a pilot to snatch the cable tethered to the balloon and lift a person off the ground. Once airborne, the crew would winch the cable in and retrieve the personnel though the back of the aircraft. This technique was discontinued for training purposes after the death of a SEAL at NAB Coronado on a training lift. The teams still utilize the Fulton Skyhook for equipment extraction and retain the capability for war if an extreme situation requires it.
During the Korean War, the UDTs operated on the coasts of North Korea, with their efforts initially focused on demolitions and mine disposal. Additionally, the UDT accompanied South Korean commandos on raids in the North to demolish railroad tunnels and bridges. The higher-ranking officers of the UDT frowned upon this activity because it was a non-traditional use of the Naval forces, which took them too far from the water line. Due to the nature of the war, the UDT maintained a low operational profile. Some of the better-known missions include the transport of spies into North Korea, and the destruction of North Korean fishing nets.
A more traditional role for the UDT was in support of Operation CHROMITE, the amphibious landing at Inchon. UDT 1 and UDT 3 divers went in ahead of the landing craft, scouting mud flats, marking low points in the channel, clearing fouled propellers, and searching for mines. Four UDT personnel acted as wave-guides for the Marine landing.
The UDT assisted in clearing mines in Wonsan harbor, under fire from enemy shore batteries. Two minesweepers were sunk in these operations. A UDT diver dove on the wreck of USS Pledge: the first U.S. combat operation with SCUBA.
The Korean War was a period of transition for the men of the UDT. They tested their previous limits and defined new parameters for their special style of warfare. These new techniques and expanded horizons positioned the UDT well to assume an even broader role as the storms of war began brewing to the south in Vietnam.
The Navy entered the Vietnam War in 1958, when the UDTs delivered a small watercraft far up the Mekong River into Laos. In 1961, naval advisers started training UDT in South Vietnam. The men were called the Liên Đoàn Người Nhái (LDNN), roughly translated as the "soldiers that fight under the sea."
Later, the UDTs supported the Amphibious Ready Groups operating on South Vietnam's rivers. UDTs manned riverine patrol craft and went ashore to demolish obstacles and enemy bunkers. They operated throughout South Vietnam, from the Mekong Delta (Sea Float), The Parrot Beak and French canal AO's through I Corps and the Song Cui Dai Estuary south of Danang.
In the mid-1950s, the Navy saw how the UDT's mission had expanded to a broad range of "unconventional warfare", but also that this clashed with the UDT's traditional focus on swimming and diving operations. It was therefore decided to create a new type of unit that would build on the UDT's elite qualities and water-borne expertise, but would add land combat skills, including parachute training and guerrilla/counterinsurgency operations. These new teams would come to be known as the US Navy SEALs (which stood for SEa, Air, and Land). Initially there was a lag in the unit's creation until President John F. Kennedy took office. Kennedy recognized the need for unconventional warfare, and supported the use of special operations forces against guerrilla activity. The Navy moved forward to establish its new special operations force and in January 1962, SEAL Team One was commissioned. The SEALs quickly earned a reputation for valor and stealth in Vietnam, where they conducted clandestine raids in perilous territory. Since then, teams of SEALs have taken on shadowy missions in strife-torn regions around the world, stalking high-profile targets such as Panama's Manuel Noriega and Colombian drug lord Pablo Escobar and playing integral roles in the wars in Iraq and Afghanistan. 
For those who served in an Underwater Demolition Team, the U.S. Navy authorized the Underwater Demolition operator badge in 1970. However, the UDT badge was phased out in 1971, a few months after it appeared, as was the silver badge for enlisted UDT/SEAL frogmen. After that, SEAL and UDT operators, both officer and enlisted, all wore the same gold Trident, as well as gold Navy jump wings. https://en.wikipedia.org/wiki/Special_Warfare_insignia
- The Frogmen (1951). This film starring Dana Andrews and Richard Widmark was based on the UDT teams. The film was set in World War II, and contemporary UDT members appeared in several sequences.
- United States Naval Special Warfare Command
- Former United States special operations units
- Underwater demolition
- United States Navy SEALs
- United States Special Operations Forces
- Republic of Korea Naval Special Warfare Flotilla
- "Commemorating The Birthplace of UDT-SEAL Teams: Waimanalo, Hawaii | National Navy UDT-SEAL Museum". Navysealmuseum.com. 2013-11-11. Retrieved 2014-05-12.
- "SEAL History: Before the First Mercury Splashdown | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 2014-05-12.
- Cunningham, Chet (2004). The Frogmen of World War II: An Oral History of the U.S. Navy's Underwater Demolition Teams. Pocket Star. ISBN 978-0-7434-8216-5.
- "Navy SEAL History". Retrieved 25 January 2008.
- Bruce Meyers, Swift, Silent, and Deadly: Marine Amphibious Reconnaissance in the Pacific, 1942-1945, 2004
- p.34 Dockery, Kevin & Brutsman, Bud Navy SEALs A History of the Early Years Berkely Publishing 2001
- p.p 30-31 Dockery & Brutsman
-  Naval Combat Demolition Units
- "World War II Era Beach Obstacles and Hedgehogs from Original NCDU School | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 2014-05-12.
- Seabee magazine online 
- "Bruce F. Meyers, Swift, Silent, and Deadly"
- Commander, V Amphibious Corps to CinCPac, report, Underwater Demolition Teams, Recommendations Concerning-Based on Experience in Flintlock (Kwajalein), 2 June 1944, declassified from secret.
-  Seals At War, Edwin P. Hoyt, Dell Books, 666 Fifth Ave, N.Y.,N.Y., 10103, 1993
-  Seals At War, Edwin P. Hoyt, Dell Books, 666 Fifth Ave, N.Y.,N.Y., 10103, 1993
-  Seals At War, Edwin P. Hoyt, Dell Books, 666 Fifth Ave, N.Y.,N.Y., 10103, 1993
- Seabee online magazine- this week in Seabee History
- Butler FK (2004). "Closed-circuit oxygen diving in the U.S. Navy". Undersea Hyperbaric Medicine. 31 (1): 3–20. PMID 15233156. Retrieved 18 March 2009.
- Hawkins T (1st Quarter 2000). "OSS Maritime". The Blast. 32 (1). Check date values in:
- Vann RD (2004). "Lambertsen and O2: beginnings of operational physiology". Undersea Hyperb Med. 31 (1): 21–31. PMID 15233157. Retrieved 18 March 2009.
- Vann RD (Spring 2000). "The evolution of diving in UDT from WW II through Korea". Fire-in-the-Hole (Official publication of the UDT-SEAL Museum).
- "Cmdr. doug fane navy udt leader". Retrieved 6 December 2009.
- "SEAL History: Underwater Demolition Teams in the Korean War | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 2014-05-12.
- "Navy UDT-SEAL Museum:History,Korea". Retrieved 25 January 2008.
- "SEAL History: Vietnam-The Men With Green Faces | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 2014-05-12.
- Boynton, Mack (2010). A Founding Father of the Navy SEALs (PDF).
- Altman, Alex (Apr 27, 2009). "A Brief History of: The Navy SEALs". TIME Magazine. Retrieved 12 May 2013.
- Mack Boynton (4th Quarter 2007). "SEAL Story of - SEAL Teams". The Blast. UDT-SEAL Association. Retrieved 6 December 2009. Check date values in:
- Best, Herbert. The Webfoot Warriors; The Story of UDT, the U.S. Navy's Underwater Demolition Team. New York: John Day Co, 1962. OCLC 1315014
- Fane, Francis Douglas, and Don Moore. The Naked Warriors: The Story of the U.S. Navy's Frogmen. Annapolis, MD: Naval Institute Press, 1995. ISBN 1557502668 OCLC 33007811
- O'Dell, James Douglas. The Water Is Never Cold: The Origins of the U.S. Navy's Combat Demolition Units, UDTs, and SEALs. Washington, DC: Brassey's, 2000. ISBN 1574882759 OCLC 44764036
- Young, Darryl. SEALs, UDT, Frogmen: Men Under Pressure. New York: Ivy Books, 1994. ISBN 0804110646 OCLC 31815574
- Navy UDT-SEAL Museum
- NavyFrogMen.com U. S. Naval Special Warfare Archives
- Pritzker Military Museum & Library
- "TNT Divers" Popular Mechanics, November 1945, pp. 72–73, one of earliest articles on WW2 UDT units.