Underwater Demolition Team

The Underwater Demolition Teams (UDT) were a special-purpose force established by the United States Navy during World War II. They came to be considered more elite and tactical during the Korean and Vietnam Wars. Their primary WWII function began with the reconnaissance and removal of natural or man-made obstacles on beaches prior to amphibious landings. They later were assigned to assist in the recovery of Space capsules/astronauts after splash down in the Mercury and Apollo space flight programs.[2] The United States Navy's Underwater Demolition Teams were pioneers in underwater demolition, closed-circuit diving, combat swimming, and midget submarine (dry and wet submersible) operations. Commando training was added making them the forerunner to the United States Navy SEAL program that exists today.[3]

Underwater Demolition Teams
Patch of the Underwater Demolition Teams.
Active15 August 1942  1 January 1983
CountryUnited States
BranchUnited States Navy
TypeAmphibious warfare
Garrison/HQFort Pierce, Florida, U.S.
Maui, Hawaii, U.S.
Nickname(s)UDT, Frogmen
EngagementsOperation Overlord
Operation Torch
Battle of Kwajalein
Battle of Roi Namur
Battle of Saipan
Battle of Tinian
Battle of Guam
Battle of Peleliu
Battle of Iwo Jima
Battle of Okinawa
Borneo campaign
Battle of Leyte
Invasion of Lingayen Gulf
Operation Beleaguer
Korean War
Vietnam War

In 1983, after additional SEAL training, the UDTs were re-designated as SEAL Teams or Swimmer Delivery Vehicle Teams (SDVTs). SDVTs have since been re-designated SEAL Delivery Vehicle Teams.[4]

Early history

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 to Army Second Lieutenant Lloyd E. Peddicord being assigned the task of analyzing the need for a human intelligence (HUMINT) capability.[3]

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.[3]

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.[3] After that experience, Rear admiral Kelley Turner, Commander of the V Amphibious Corps (VAC), 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.[5]

Later in war, the Army Engineers passed down demolition jobs to the U.S. Navy. It then became the Navy's responsibility to clear any obstacles and defenses in the near shore area.

A memorial to the founding of the UDT has been built at Bellows Air Force Station near the original Amphibious Training Base (ATB) Waimanalo.

In early 1942 it became apparent that the Navy needed that capability to destroy submerged obstacles, natural or man-made, for amphibious landings. 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.[6] 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.

In early May 1943, a two-phase "Naval Demolition Project" was directed by the Chief of Naval Operations (CNO) "to meet a present and urgent requirement". The first phase began at Amphibious Training Base (ATB) Solomons, Maryland with the establishment of Operational Naval Demolition Unit No. 1. Six Officers and eighteen enlisted men reported from NTC Camp Peary dynamiting and demolition school for a four-week course.[7][8] Those Seabees were immediately sent to participate in the invasion of Sicily[9] where they were divided in three groups that landed on the beaches near Licata, Gela and Scoglitti.[10]

Later in 1943 the Navy decided to create a component dedicated to the removal of amphibious obstructions. It was to be known as a Naval Combat Demolition Unit (NCDU) consisting of one junior Civil Engineer Corps (CEC) officer and five enlisted. A NCDU was to clear beach obstacles for an invasion force with the team coming ashore in an LCRS inflatable boat.[11] On May 7, Admiral Ernest J. 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 between May and mid-July.[12] From Camp Peary the NCDU training was moved to Fort Pierce with the first class beginning there mid-July. Despite the move, Camp Peary was Kauffman's primary source of manpower. "He would go up to Camp Peary's Dynamite School and assemble the Seabees in the auditorium saying: "I need volunteers for hazardous, prolonged and distant duty."[13] Kauffman's other volunteers came from 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, leaving Kauffman with the boys."[14] It was and is still considered the first "Hell Week."


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 Operation Overlord. All told, the NCDUs had 34 teams in England for the invasion of Normandy. While waiting for D-day the NCDUs trained with the 146th, 277th and 299th Combat Engineer Battalions.[15] Each NCDU had 5 men from a Combat Engineer Battalion attached to the team. In the beginning the first 10 NCDUs were split into 3 groups.[15] Initially it was somewhat ad-hoc as they had no Commanding Officer, but the Senior officer was the leader of group III, Lieutenant Smith (CEC). He served in that capacity unofficially for the entire group.[15] His group III performed numerous experimental demolitions work and developed the Hagensen Pack.[15](an innovation that used 2.5-pound (1.1 kg) of tetryl placed into rubber tubes that could be twisted around obstacles)[16] As more teams arrived a NCDU Command was created for the invasion. The NCDUs at Normandy were numbers: 11, 22-30, 41-46, 127-8, 130-42[15]

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 on 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.[5] Overall, NCDUs had 53 percent casualties.

NCDUs also participated in Operation Dragoon, the invasion of southern France.

With Europe invaded Admiral Turner requisitioned all available NCDUs from Fort Pierce for integration into the UDTs for the Pacific. However, the first NCDUs, 1-10, had been staged at Turner City, Florida Island in the Solomon Islands during January 1944.[17] A few were temporarily attached to UDTs.[17] Later NCDUs 1-10 were combined to form Underwater Demolition Team Able.[17] This team was disbanded with NCDUs 2 and 3, plus three others assigned to MacArthur's 7th Amphibious force, and were the only NCDUs remaining at war's end. The other men from Team Able were assigned to numbered UDTs.

Underwater Demolition Teams

The first units that were designated as Underwater Demolition Teams were formed in the Pacific Theater. Rear Admiral Turner, the Navy's top amphibious expert, ordered the formation of nine Underwater Demolition Teams. The personnel for these teams were mostly Seabees that had started out in the UCDUs. UDT training was at Waimānalo, Hawaii, under V Amphibious Corps operational and administrative control. Most of the instructors and trainees were graduates of the Fort Pierce NCDU or Scouts and Raiders schools, Seabees, Marines, and Army soldiers. Under the direction of Marine Corps Amphibious Reconnaissance Battalion, UDTs 1 and 2 were hastily trained for their Kwajalein mission in January 1944.[6] The training made use of inflatable boats and included some swimming. The teams 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. At that time the men in the teams wore fatigues, boots and helmets. They were lifelined to their boats and stayed out of the water as much as possible.

The UDTs were organized with approximately sixteen officers and eighty men each. One Marine and one Army officer were liaisons within each team.[18] They were deployed in every major amphibious landing after Tarawa with 34 teams eventually being commissioned. The last teams created for the invasion of Japan were spared deployment by the atomic bombing of Japan. When it was over, teams 1-21 were the teams that had deployed operationally, meaning that slightly over half of the operational UDTs came from the Seabees.

Prior to Operation Galvanic and Tarawa, V Amphibious Corps had identified coral as an issue for future amphibious operations. Rear Admiral Turner, Commander, V Amphibious Corps, had ordered a review to address the problem. VAC found that the only people having any applicable experience with the material were men in the Naval Construction Battalions. The Admiral tasked Lt. Thomas C. Crist (CEC) to develop a method for blasting coral under combat conditions and putting together a team for that purpose.[19] LT Crist started by contacting others he had blasted coral with in CB 5 and by the end November 1943 he had assembled close to 30 officers and 150 enlisted men, at Waipio Amphibious Operating Base on Maui.[19]


The invasion of Tarawa in November 1943 nearly met disaster due to unseen obstructions in the water. Tarawa lies in eastern Micronesia and had an unusual neap tide 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 wade several hundred yards to shore while wearing full packs, under heavy fire across treacherously uneven coral. 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.

Kwajalein, Roi-Namur, Saipan, Tinian, Guam

The next operation was to be Kwajalein and the plan calling for night reconnaissance. However, Rear Admiral Turner did not want a repeat of Tarawa. He wanted to know about coral and any obstacles the Japanese may have emplaced. To find this out the men that Lt Crist had staged were used to form UDT 1 and UDT 2. The team commanders were Cmdr. E.D. Brewster (CEC) UDT 1 and Lt. Crist UDT 2 (Lt. Crist was replaced and made Ops officer because Admiral Conolly wanted a commander with combat experience). UDT 1 was ordered to perform two daylight recons.[20] The missions were to follow the standard Fort Pierce procedure with each two-man team getting close to the beach in a rubber boat, wearing combat fatigues, boots, helmets, and life jackets, and make their observations. Team 1 found that the reef kept them from acertaining conditions both in the water and on the beach. 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. Ensign Lewis F. Luehrs and Seabee Chief Bill Acheson had anticipated that they would not be able to carry out the assignment following Fort Pierce protocol and had worn swim trunks beneath their fatigues.[20] Stripping down, they swam 45 minutes undetected across the reef returning with sketches of gun emplacements and other intelligence. Still in their trunks, they were taken directly to Rear Admiral Turner's flagship to report.[20] Afterwards, Rear Admiral Turner concluded that the only way to get this kind of information was to do what these men had done as individual swimmers, which is what he relayed to Admiral Nimitz. The planning and decisions of Rear Admiral Turner, Ensign Lehrs and Chief Achenson made Kwajalein a developmental day in UDT history, changing both the mission model and training regimen. Seabees made up the majority of the men in teams 1–9, 13 and 15. The Officers of those teams were primarily CEC[21] (Seabees). UDT 2 was sent to Roi-Namur where Lt. Crist would earn a Silver Star. UDTs 1 and 2 were decommissioned upon return to Hawaii with the men transferred to UDTs 3, 4, 5, and 6. Admiral Turner ordered the formation of nine teams, three for III Amphibious Corps and six for V Amphibious Corps(in all teams 3-11). As more NCDUs arrived in the Pacific they were used to form even more teams. UDT 15 was an all NCDU team. It became obvious more men were needed than the NCDUs would supply and Cmdr. Kauffman was no longer recruiting Seabees, so Admiral Nimitz put out a call to the Pacific Fleet for volunteers. They would form three teams, UDT 14 would be the first of them. Recruiting was such an issue that that three Lt Cmdrs where transferred from USN Beach Battalions to command UDTs 11, 12, 13 that had no background in demolition.

After Kwajalein, the UDTs created the Naval Combat Demolition Training and Experimental Base at Kihei, expanding upon what had been learned from UDT 1. Operations began in February 1944 with Lt Crist the head of training. Most of the procedures from Fort Pierce were changed replaced with an emphasis on developing swimmers, daylight reconnaissance, and no lifelines. The uniform of the day changed to diving masks, swim trunks, and a Ka-bar, creating the UDT image as "Naked Warriors"(swim-fins were added after UDT 10 introduced them). Lt. Crist was head of training a very short time before he was made commander of UDT 3. In April, Lt. Cmdr. Kauffman was transferred from Fort Pierce to command UDT 5 and serve as senior staff officer, Underwater Demolition Teams, Amphibious Forces, as well as be the Underwater Demolition Training Officer, Amphibious Training Command.

At Saipan and Tinian UDTs 5, 6, & 7 were given the call. The missions were daylight for Saipan and night for Tinian. At Saipan UDT 7 developed a method to recover swimmers on the move without making the recovery vessel a stationary target.

For Guam UDTs 3, 4, & 6 were assigned the mission. When it was over the Seabee dominated teams had made naval history.[22] For the Marianas operations Admiral Turner recommended over sixty Silver Stars and over three hundred Bronze Stars with Vs for UDTs 3-7[22] That was unpresendented in U.S. Naval/Marine Corps history.[22] For UDTs 5 and 7 every officer received a silver star and all the enlisted received bronze stars with Vs for Operation Forager (Tinian).[23] For UDTs 3 and 4 every officer received a silver star and all the enlisted received bronze stars with Vs for Operation Forager (Guam).[23] Admiral Richard Lansing Conolly felt the commanders of teams 3 and 4 (Lt. Crist and Lt. W.G. Carberry) should have received Navy Crosses.[23] While the officers and enlisted were individually treated equally in those awards UDTs 4 & 7 also received Naval Unit Commendations while UDTs 3 & 5 received no unit recognition.

Peleliu, Philippines, and Iwo Jima

UDTs 6, 7, and 10 drew the Peleliu[24] assignment while UDT 8 went to Angaur. The officers were almost all CEC and the enlisted were Seabees.[25]

At formation UDT 10 was assigned 5 officers and 24 enlisted that had trained as OSS Operational Swimmers.(Maritime Unit: Operational Swimmer Group II) They were led by a Lt. A.O. Chote Jr., who became UDT 10's commanding officer.The men were multi-service: Army, Coast Guard, Marine Corps and Navy.[26][27] but, the OSS was not allowed to operate in the Pacific Theater. Admiral Nimitz needed swimmers and did approve their transfer from the OSS to his operational and administrative control. Most of their OSS gear was stored as it was not applicable to UDT work however, their swimfins came with them. The other UDTs quickly adopted them.

UDT 14 was the first all-Navy team (one of three from the Pacific fleet) even though it's CO amd XO were CEC and some of Team Able was incorporated. In the Philippines Leyte Gulf UDTs 10 & 15 reconnoitered beaches at Luzon, teams 3, 4, 5, & 8 were sent to Dulag and teams 6, 9, & 10 went to Tacloban. When UDT 3 returned to Maui the team was made the instructors of the school.[28] Lt Crist was again made Training Officer. Under his direction training was broken into four 2 week blocks with an emphasis on swimming and reconnaissance.[28] There were classes in night operations, unit control, coral and lava blasting in addition to bivouacking, small unit tactics and small arms.[28] Lt Crist would be promoted to Lt Cmdr and the team would remain in Hawaii until April of 1945.[28] At that time the Seabees of UDT 3 were transferred to Fort Pierce to be the instructors there.[28] In all they would train teams 12 to 22.[28] Lt. Cmdr. Crist would be sent back to Hawaii.

D-minus 2 at Iwo Jima UDTs 12, 13, 14, and 15 reconnoitered the beaches from twelve LCI(G) with just one man wounded. They did come under intense heavy fire that sank three of their LCI(G) with the others seriously damaged of disabled. The LCI(G) crews suffered more that the UDTs with the skipper of one boat earning a Medal of Honor. The next day a Japanese bomb hit UDT 15's APD, USS Blessman killing fifteen and wounding 23. It was the largest loss suffered by the UDTs during the war. On D-plus 2 the beachmaster requested help. There were so many broached or damaged landing craft and the beach was so clogged with war debris that there was no place for landing craft to get ashore. Lt Cmdr. E. Hochuli of UDT 12 volunteered his team to go deal with the problem and teams 13 and 14 were ordered to go with.[29] Lt Cmdr. Vincent Moranz of UDT 13 was "reluctant, and radioed that his men ... were not salvage-men.[29] It is reported that Capt. (Bull) Hanlon, Underwater Demolition Operations Commanding Officer radioed back that he didn't want anything salvaged, he wanted that beach cleared."[29] The differance in attitude between Hochuli and Moranz would be remembered in the unit awards. The three teams worked for five days clearing the waters edge. While the teams all did the same job under the same conditions[29] the Navy gave them different unit awards: UDT 12 a PUC, UDT 14 a NUC and UDT 13 nothing. The USMC ground commanders felt that every man that set foot on the island during the assault had an award coming. The Navy did not share this point of view, besides UDT 13 not a single USN beach party received an unit award either. On D-plus 2, when the UDTs set foot on beaches that were under a USMC assault, any unit award they received should have come under the USMC award protocol. The USMC Iwo Jima PUC/NUC was a mass award with the PUC going to assault units and the NUC going to support units.

UDTs also served at Eniwetok, Ulithi, Leyte, Lingayen Gulf, Zambales, Labuan, and Brunei Bay. At Lingayen UDT 9 was aboard the USS Belknap when she was hit by a Kamikaze. It cost the team one officer, 7 enlisted, 3 MIA and 13 wounded.


The largest UDT operation of WWII was the invasion of Okinawa, involving teams 7, 11, 12, 13, 14, 16, 17, and 18(nearly 1,000 men). All prior missions had been in warm tropic waters but, the waters around Okinawa were cool enough that long immersion could cause hypothermia and severe cramps. Since thermal protection for swimmers was not available, UDTs were at risk to these hazards working around Okinawa. Operations included both real reconnaissance and demolition at the landing beaches, and feints to create the illusion of landings in other locations. Pointed poles set into the coral reef protected the beaches on Okinawa. Teams 11 and 16 were sent in to blast the poles. The charges 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. UDT 11 went back the next day and took out the remaining poles after-which the team remained to guide landing-craft to the beach.

At wars end 34 teams had been formed with teams 1–21 having actually been deployed. The Seabees provided half of the men in the teams that saw service. The U.S. Navy did not publicize the existence of the UDTs until post war and when they did they gave credit to Lt. Commander Kauffman and the Seabees.[30] During WWII the Navy did not have a rating for the UDTs nor did they have an insignia. Those men with the CB rating on their uniforms considered themselves Seabees that were doing underwater demolition. They did not call themselves "UDTs" or "Frogmen" but rather "Demolitioneers" which had carried over from the NCDUs[31] and LtCdr Kauffmans recruiting them from the Seabee dynamiting and demolition school. UDTs had to meet the military's standard age guidelines, Seabees older could not volunteer. In preparation for the invasion of Japan the UDTs created a cold water training center and mid-1945 UDTs had to meet a new physical standard. UDT 9 lost 70% of the team to this change. The last UDT demolition operation of the war was on 4 July 1945 at Balikpapan, Borneo. The UDTs continued to prepare for the invasion of Japan until VJ Day when their role in the Pacific came to an end. With the draw-down from the war two half-strength UDTs were retained, one on each coast: UDT Baker and UDT Easy.

After World War II

Japan occupation

On 20 August 1945 USS Begor embarked UDT 21 at Guam as a component of the U.S. occupation force heading for Japan.[32] Nine days later UDT 21 became the first U.S military unit to set foot on Japanese home soil when it reconned the beaches at Futtsu-misaki Point in Tokyo Bay.[32] The assessment was that the area was well suited for landing U.S. amphibious forces. The next day Begor took UDT 21 to Yokosuka Naval Base.[32] There the team cleared the docks for the first U.S. warship to dock in Japan, USS San Diego.[32] The team remained in Tokyo Bay until 8 Sept when it was tasked with locating remaining Kamikaze and two man submarines at Katsura Wan, Uchiura Wan at Suruga Bay, Sendai, Onohama Shipyards and Choshi.[32] Orders arrived for Begor to return the team to San Diego on 27 September.[32]

From September 21–26 UDT 11 was at Nagasaki and reported men getting sick from the stench.[33]


With the war over thousands of Japanese troops remained in China. The issue was given to the Marine's III Marine Amphibious Corps. UDT 9 was assigned to Operation Beleaguer to recon the landings of the 1st Marine Division at Taku and Tsingtao the first two weeks of October 1945.[34] On their way to China the Navy had UDT 8 carry out a mission at Jinaen, Korea September 8–27, 1945.[34] When UDT 9 arrived back in the States it was made one of the two post-War teams and redesignated UDT Baker.[34]

UDT 8 was also sent to China and was at Taku, Chefoo, and Tsingtao.[35]

Operation Crossroads

Bikini atoll was chosen for the site of the nuclear tests of Operation Crossroads.

"In March 1946, Project Y scientists from Los Alamos decided that the analysis of a sample of water from the immediate vicinity of the nuclear detonation was essential if the tests were to be properly evaluated. After consideration of several proposals to accomplish this, it was finally decided to employ drone boats of the type used by Naval Combat Demolition Units in France during the war".[36]

UDT Easy, later named UDT 3, was given the designation TU 1.1.3 for the Operation and was assigned the control and maintenance of the drone boats. On 27 April, 7 officers and 51 enlisted men embarked the USS Begor at the Seabee base Port Hueneme, CA,[36] for transit to Bikini. At Bikini the drones were controlled from the Begor . Once a water sample was taken the drone would return to the Begor to be hosed down for decontamination. After a Radiation Safety Officer had taken a Geiger counter reading and the OK given, the UDTs would board with a radiation chemist to retrieve the sample.[37] Begor came to have the reputation as the most contaminated boat in the fleet.[37]

A major issue afterwards was the treatment of the dislocated natives. In November 1948, the Bikinians were relocated to the uninhabited Island of Kili, however that island was located inside a coral reef that had no channel for access to the sea.[38] In the spring of 1949, the Governor of the Trust Territories, Marshall Group requested the U.S. Navy blast a channel to change this.[38] That task was given to the Seabees on Kwajalin whose CO quickly determined this was actually a UDT project.[38] He sent a request to CINCPACFLT who forwarded it to COMPHIBPAC.[38] This ultimately resulted in the sending of UDT 3 on a Civic action program that turned out better than politicians could have hoped. The King of the Bikinians held a send off feast for the UDTs the night before they departed.[38]

Submersible Operations

Even 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.[39][40] 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.[39][41] 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 the new equipment be too dangerous. Nonetheless, LCDR 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, LCDR Fane and Dr. Lambertsen demonstrated new UDT capabilities with a successful lock-out and re-entry from USS Grouper, 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 Lieutenant (junior grade) Bruce Dunning.[39][42]

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 Dr. Lambertsen.

It was at this time that the UDT, led by LCDR Fane, established training facilities at Saint Thomas in the Virgin Islands.[43]

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 Skyhook for equipment extraction and retain the capability for war if an extreme situation requires it.

Korean War

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.[44]

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 using SCUBA gear.

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 war began brewing to the south in Vietnam.[45]

Vietnam War

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), which translates as "Frogmen Team."

The UDT also carried out hydrographic surveys in South Vietnam's coastal waters.[46]

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.

Birth of Navy SEALs

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.[47] These new teams would come to be known as the US Navy SEALs, an acronym 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 commissioned SEAL Team ONE in NAB Coronado and SEAL Team TWO at NAB Little Creek. UDT-11 & 12 were still active on the west coast and UDT-21 & 22 on the east coast. The SEALs quickly earned a reputation for valor and stealth in Vietnam, where they conducted clandestine raids in perilous territory. In May 1983, the remaining UDT teams were reorganized as SEAL teams. UDT 11 became SEAL Team Five and UDT 12 became Seal Delivery Vehicle Team One. UDT 21 became SEAL Team Four and UDT 22 became Seal Delivery Vehicle Team Two. A new team, SEAL Team Three was established in October 1983. Since then, teams of SEALs have taken on clandestine missions in war-torn regions around the world, tracking 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.[48][49]


UDT Badges
Officer Underwater Demolition Badge
Enlisted Underwater Demolition Badge

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.[50]

Unit awards

The UDTs have received several unit citations and commendations. Members who participated in actions that merited the award are authorized to wear the medal or ribbon associated with the award on their uniform. Awards and decorations of the United States Armed Forces have different categories, (i.e. Service, Campaign, Unit, and Personal). Unit Citations are distinct from the other decorations.[51]

Naval Combat Demolition Force O (Omaha beach) Normandy

Naval Combat Demolition Force U (Utah beach) : Normandy




UDT 11

UDT 12

UDT 13

UDT 14

UDT 21

UDT 22


See also


  1. "Commemorating The Birthplace of UDT-SEAL Teams: Waimanalo, Hawaii | National Navy UDT-SEAL Museum". Navysealmuseum.com. 11 November 2013. Retrieved 12 May 2014.
  2. "SEAL History: Before the First Mercury Splashdown | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 12 May 2014.
  3. 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.
  4. "Navy SEAL History". Retrieved 25 January 2008.
  5. "SEAL History: Origins of Naval Special Warfare-WWII | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 12 May 2014.
  6. Meyers, Bruce F. (2004). Swift, Silent, and Deadly: Marine Amphibious Reconnaissance in the Pacific, 1942–1945. Naval Institute Press.
  7. Blazich, Frank A. (12 May 2017). "This Week in Seabee History (Week of May 14)". Seabee Online. Navy Facilities Engineering Command. Retrieved 18 October 2017.
  8. Blazich, Frank A. (6 June 2014). "Opening Omaha Beach: Ensign Karnowski and NCDU-45". Seabee Online. Navy Facilities Engineering Command. Retrieved 18 October 2017.
  9. "Seal History: Origins of Naval Special Warfare – WWII". Navy Seal Museum Archives. Retrieved 18 October 2017.
  10. pp. 30-31 Dockery & Brutsman
  11. p.34 Dockery, Kevin & Brutsman, Bud Navy SEALs A History of the Early Years Berkely Publishing 2001
  12. "Naval Combat Demolition Units". SpecWarNet.net. Retrieved 1 March 2018.
  13. Erickson, Mark St. John (3 December 2017). "Training the Fighting Seabees of WWII at Camp Peary". Daily Press. Newport News, Virginia.
  14. Hornfischer, James D. (2017). The Fleet at Flood Tide: America at Total War in the Pacific, 1944–1945. New York: Bantam Books. p. 44.
  15. REPORT ON NAVAL COMBAT DEMOLITION UNITS in OPERATION "NEPTUNE" as part of TASK FORCE 122, Submitted by: Lt.(jg) H. L. Blackwell, Jr. D-V(G) , USNR, 5 July, 1944
  16. "World War II Era Beach Obstacles and Hedgehogs from Original NCDU School | National Navy UDT-SEAL Museum". NavySealMuseum.com. Retrieved 12 May 2014.
  17. Liptak, Eugene (2014). World War II US Navy Special Warfare Units. New York: Osprey Publishing. p. 25.
  18. Commander, V Amphibious Corps to CinCPac, report, Underwater Demolition Teams, Recommendations Concerning-Based on Experience in Flintlock (Kwajalein), 2 June 1944, declassified from secret.
  19. The Water Is Never Cold, James Douglas O'Dell, 2000, p. 132, Brassey's, 22841 Quicksilver Drive, Dulles, Va. 20166, ISBN 1-57488-275-9
  20. Hoyt, Edwin P. (1993). Seals At War. New York, New York: Dell Books.
  21. Blazich, Frank A., Jr. (12 September 2016). "This Week in Seabee History". Seabee Online. Navy Facilities Engineering Command.
  22. "America's First Frogman", Elizabeth K. Bush, Naval Institute Press, 291 Wood Road, Annapolis, Maryland, 2012, Chapt. 7, ISBN 978-1-61251-298-3
  23. Naked Warriors, Cdt. Francis Douglas Fane USNR (Ret.), St. Martin's Press, 175 Fifth Ave, New York, NY 10010, 1996, pp. 122, 131, ISBN 0-312-95985-0
  24. Amphibious Assault: Key to the World War II Battle for Peleliu, Toni L. Carrell, Ph.D, Office of Ocean Exploration and Research, National Oceanic and Atmospheric Administration, U.S. Department of Commerce web site
  25. This Week in Seabee History, Sept 10-17, for Sept 12, Seabee Magazine online
  26. OSS in Action The Pacific and the Far East, Series: OSS Training in the National Parks and Service Abroad in World War II, Catoctin Mountain Park, Prince William Forest Park webpage, August 8, 2017, National Park Service, 1100 Ohio Drive, SW, Washington, DC 20242
  28. "The Teams in World War II". View of the Rockies. Retrieved 18 October 2017.
  29. UDT 13, The Men From Fort Pierce(excerpts), Marvin Cooper, U. S. Naval Special Warfare Archives web-site
  30. UNDERWATER DEMOLITION, "ALL HANDS", The Bureau of Naval Personal Information Bulletin, October 1945, NAVPERS-0 NUMBER 343 pp. 12–15
  31. NCDU 216 Photo, National Navy UDT–SEAL Museum, North Hutchinson Island, Fort Pierce, FL
  32. USS BEGOR (APD-127) veterans webpage
  33. UDT 11, U. S. Naval Special Warfare Archives web site, "The Men From Fort Pierce" by Marvin Cooper
  34. UNDERWATER DEMOLITION TEAM HISTORIES, WWII UDT TEAM NINE, compiled by Robert Allan King for the UDT-SEAL Museum from public records at the Operational Archives of the Naval Historical Center, U. S. Naval Special Warfare Archives web-site
  35. UNDERWATER DEMOLITION TEAM HISTORIES, WWII UDT TEAM EIGHT, compiled by Robert Allan King for the UDT-SEAL Museum from public records at the Operational Archives of the Naval Historical Center, U. S. Naval Special Warfare Archives web-site
  36. Operations Crossroads, DNA 6032F, prepared by the Defense Nuclear Agency, p.189-90
  37. USS BEGOR (APD-127) Veterans webpage
  38. U.S. Naval Special Warfare Archives, After Operation Crossroads – Kili Island, Mack M. Boynton, December 21, 2013
  39. Butler FK (2004). "Closed-circuit oxygen diving in the U.S. Navy". Undersea and Hyperbaric Medicine. 31 (1): 3–20. PMID 15233156. Retrieved 18 March 2009.
  40. Hawkins T (2000). "OSS Maritime". The Blast. 32 (1).
  41. Vann RD (2004). "Lambertsen and O2: beginnings of operational physiology". Undersea Hyperb Med. 31 (1): 21–31. PMID 15233157. Retrieved 18 March 2009.
  42. Vann RD (Spring 2000). "The evolution of diving in UDT from WW II through Korea". Fire-in-the-Hole.
  43. "CDR Doug Fane, Navy Udt leader". bigislandforum.org. Retrieved 6 December 2009.
  44. "SEAL History: Underwater Demolition Teams in the Korean War | National Navy UDT-SEAL Museum". Navysealmuseum.com. Retrieved 12 May 2014.
  45. "Navy UDT-SEAL Museum: History, Korea". navysealmuseum.com. Retrieved 25 January 2008.
  46. "SEAL History: Vietnam-The Men With Green Faces | National Navy UDT-SEAL Museum". Navysealmuseum.com. Archived from the original on 10 November 2014. Retrieved 12 May 2014.
  47. Boynton, Mack (2010). A Founding Father of the Navy SEALs (PDF).
  48. Altman, Alex (27 April 2009). "A Brief History of: The Navy SEALs". TIME Magazine. Retrieved 12 May 2013.
  49. Mack Boynton (2007). "SEAL Story of - SEAL Teams". The Blast. UDT-SEAL Association. Retrieved 6 December 2009.
  50. Special Warfare insignia
  51. List of Award Abbreviations, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
  52. Naval History and Heritage Command website, Part 2 - Unit Awards, Published:Mon Aug 31 14:01:11 EDT 2015, p. 22
  53. US Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
  54. US Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
  55. US Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
  56. US Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350

Further reading

  • 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
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