Underwater Demolition Teams (UDT), or

frogmen A frogman is someone who is trained in scuba diving or swimming underwater in a tactical capacity that includes military, and in some European countries, police work. Such personnel are also known by the more formal names of combat diver, comb ...

, were amphibious units created by the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

with specialized non-tactical missions. They were predecessors of the navy's current SEAL teams. Their primary WWII function began with

reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmisher ...

and underwater demolition of natural or man-made obstacles obstructing

amphibious landings Amphibious warfare is a type of offensive military operation that today uses naval ships to project ground and air power onto a hostile or potentially hostile shore at a designated landing beach. Through history the operations were conducte ...

. Postwar they transitioned to

scuba gear Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface air supply. The name "scuba", an acronym for " Self-Contained Underwater Breathing Apparatus", was coined by Chri ...

changing their capabilities. With that they came to be considered more elite and tactical during the

Korean Korean may refer to: People and culture * Koreans, ethnic group originating in the Korean Peninsula * Korean cuisine * Korean culture * Korean language **Korean alphabet, known as Hangul or Chosŏn'gŭl **Korean dialects and the Jeju language ** ...

and

Vietnam War The Vietnam War (also known by other names) was a conflict in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. It was the second of the Indochina Wars and was officially fought between North Vietnam a ...

s. UDTs were pioneers in

underwater demolition Underwater demolition refers to the deliberate destruction or neutralization of man-made or natural underwater obstacles, both for military and civilian purposes. History Charles Pasley In 1839 Charles Pasley, at the time a colonel of the Roya ...

, closed-circuit diving, combat swimming, and

midget submarine A midget submarine (also called a mini submarine) is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to six or nine, with little or no on-board living accommodation. They normally work with mother ships, ...

(dry and wet submersible) operations. They later were tasked with ensuring recovery of

space capsule A space capsule is an often-crewed spacecraft that uses a blunt-body reentry capsule to reenter the Earth's atmosphere without wings. Capsules are distinguished from other satellites primarily by the ability to survive reentry and return a payl ...

s and astronauts after splash down in the Mercury,

Gemini Gemini may refer to: Space * Gemini (constellation), one of the constellations of the zodiac ** Gemini in Chinese astronomy * Project Gemini, the second U.S. crewed spaceflight program * Gemini Observatory, consisting of telescopes in the Norther ...

and

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label= Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label ...

space flight programs.

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training was added making them the forerunner to the United States Navy SEAL program that exists today. 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.

Early history

The United States Navy studied the problems encountered by the disastrous Allied

during the Gallipoli Campaign of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

. 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 Human intelligence is the intellectual capability of humans, which is marked by complex cognitive feats and high levels of motivation and self-awareness. High intelligence is associated with better outcomes in life. Through intelligence, humans ...

(HUMINT) capability. When the U.S. entered World War II, the Navy realized that in order to strike at the

Axis powers The Axis powers, ; it, Potenze dell'Asse ; ja, 枢軸国 ''Sūjikukoku'', group=nb originally called the Rome–Berlin Axis, was a military coalition that initiated World War II and fought against the Allies. Its principal members were ...

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 Little is a synonym for small size and may refer to: Arts and entertainment * ''Little'' (album), 1990 debut album of Vic Chesnutt * ''Little'' (film), 2019 American comedy film *The Littles, a series of children's novels by American author John P ...

. In 1942, the

Army An army (from Old French ''armee'', itself derived from the Latin verb ''armāre'', meaning "to arm", and related to the Latin noun ''arma'', meaning "arms" or "weapons"), ground force or land force is a fighting force that fights primarily on ...

and Navy jointly established the Amphibious Scout and Raider School at

Fort Pierce Fort Pierce is a city in and the county seat of St. Lucie County, Florida, United States. The city is part of the Treasure Coast region of Atlantic Coast Florida. It is also known as the Sunrise City, sister to San Francisco, California, the Suns ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

. Here

Lieutenant Commander Lieutenant commander (also hyphenated lieutenant-commander and abbreviated Lt Cdr, LtCdr. or LCDR) is a commissioned officer rank in many navies. The rank is superior to a lieutenant and subordinate to a commander. The corresponding ran ...

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. The need for intelligence gathering prior to landings became paramount following the amphibious assault at the Battle of Tarawa in November 1943. Although Navy and Marine Corps planners had identified coral as an issue, they incorrectly assumed landing craft would be able to crawl over the coral. Marines were forced to exit their craft in chest deep water a thousand yards from shore, with many men drowning due to the irregularities of the reefs and

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

gunners inflicting heavy U.S. casualties. After that experience, Rear admiral Kelley Turner, Commander of the

V Amphibious Corps The V Amphibious Corps (VAC) was a formation of the United States Marine Corps which was composed of the 3rd, 4th and 5th Marine Divisions in World War II. The three divisions were the amphibious landing force for the United States Fifth Fleet ...

(VAC), directed Seabee Lt. Crist (CEC) to come up with a means to deal with the coral and the men to do it. Lt. Crist staged 30 officers and 150 enlisted men from the 7th Naval Construction RegimentSubmarine Blasting, 301 Naval Construction Battalion Cruisebook, Seabee Museum Archives website, Jan. 2020, p.60, Port Hueneme ,CA

at Waipio Amphibious Operating Base on Oahu to form the nucleus of a reconnaissance and demolition training program. It is here that the UDTs of the Pacific were born. 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) in Oahu.

Naval Combat Demolition Units

In early May 1943, a two-phase "Naval Demolition Project" was ordered 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 Solomons, also known as Solomons Island, is an unincorporated community and census-designated place (CDP) in Calvert County, Maryland, United States. The population was 2,368 at the 2010 census, up from 1,536 in 2000. Solomons is a popular weekend ...

with the establishment of Operational Naval Demolition Unit No. 1. Six Officers and eighteen enlisted men reported from the Seabees dynamiting and demolition school at

Camp Peary Camp Peary is an approximately 9,000 acre U.S. military reservation in York County near Williamsburg, Virginia. Officially referred to as an Armed Forces Experimental Training Activity (AFETA) under the authority of the Department of Defense, ...

for a four-week course. Those Seabees were immediately sent to participate in the invasion of Sicily where they were divided in three groups that landed on the beaches near Licata,

Gela Gela (Sicilian and ; grc, Γέλα) is a city and (municipality) in the Autonomous Region of Sicily, Italy; in terms of area and population, it is the largest municipality on the southern coast of Sicily. Gela is part of the Province of Ca ...

and Scoglitti. Also in May, the Navy created a Naval Combat Demolition Units (NCDUs) tasked with eliminating beach obstructions in advance of amphibious assaults, going ashore in an LCRS

inflatable boat An inflatable boat is a lightweight boat constructed with its sides and bow made of flexible tubes containing pressurised gas. For smaller boats, the floor and hull is often flexible, while for boats longer than , the floor typically consists ...

. Each NCDU consisted of five enlisted men led by a single, junior (CEC) officer. In early May, Chief of Naval Operations Admiral

Ernest J. King Ernest Joseph King (23 November 1878 – 25 June 1956) was an American naval officer who served as Commander in Chief, United States Fleet (COMINCH) and Chief of Naval Operations (CNO) during World War II. As COMINCH-CNO, he directed the Un ...

, picked Lieutenant Commander Draper L. Kauffman to lead the training. The first six classes graduated from "Area E" at the Seabee's Camp Peary between May and mid-July. Training was moved to Fort Pierce,Florida where the first class began mid-July 1943. Despite the move and having the Scouts Raiders base close by, Camp Peary was Kauffman's primary source of recruits. "He would go up to Camp Peary's Dynamite School and assemble the

Seabee , colors = , mascot = Bumblebee , battles = Guadalcanal, Bougainville, Cape Gloucester, Los Negros, Guam, Peleliu, Tarawa, Kwajalein, Saipan, Tinian, Iwo Jima, Philippin ...

s in the auditorium saying: ''"I need volunteers for hazardous, prolonged and distant duty."'' Kauffman's other volunteers came from the U.S. Marines, and U.S. Army

combat engineer A combat engineer (also called pioneer or sapper) is a type of soldier who performs military engineering tasks in support of land forces combat operations. Combat engineers perform a variety of military engineering, tunnel and mine warfare tas ...

s. 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." It was and is still considered the first " Hell Week".

Normandy

In early November 1943 NCDU-11 was assigned as the advance NCDU party for Operation Overlord. They would be joined in

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

by 33 more NCDUs. They trained with the 146th, 277th and 299th Combat Engineers to prepare for the landing. Each Unit had five

Combat engineers A combat engineer (also called pioneer or sapper) is a type of soldier who performs military engineering tasks in support of land forces combat operations. Combat engineers perform a variety of military engineering, tunnel and mine warfare tas ...

attached to it. The first 10 NCDUs divided into three groups. The senior officer, by rank, was the commanding officer of Group III,

Lieutenant A lieutenant ( , ; abbreviated Lt., Lt, LT, Lieut and similar) is a commissioned officer rank in the armed forces of many nations. The meaning of lieutenant differs in different militaries (see comparative military ranks), but it is often ...

Smith (CEC). He assumed command in an unofficial capacity. His Group III worked on experimental demolitions and developed the Hagensen Pack.(an innovation that used of

tetryl 2,4,6-Trinitrophenylmethylnitramine commonly referred to as tetryl ( C7 H5 N5 O8) is an explosive compound used to make detonators and explosive booster charges. Tetryl is a nitramine booster explosive, though its use has been largely superseded ...

placed into rubber tubes that could be twisted around obstacles) As more teams arrived a NCDU Command was created for NCDUs: 11, 22–30, 41–46, 127–8, 130–42Report 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
/ref> Naval Combat Demolition Unit 45

The Germans had constructed elaborate defenses on the French coast. These included steel posts driven into the beach and topped with explosive charges. Large 3-ton steel barricades called Belgian Gates and

hedgehogs A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family (biology), family Erinaceidae. There are seventeen species of hedgehog in five genus, genera found throughout parts of Europe, Asia, and Africa, and in Ne ...

were placed throughout the tidal zone. Behind which was a network of reinforced:

coastal artillery Coastal artillery is the branch of the armed forces concerned with operating anti-ship artillery or fixed gun batteries in coastal fortifications. From the Middle Ages until World War II, coastal artillery and naval artillery in the form of ...

, mortar and

machine gun A machine gun is a fully automatic, rifled autoloading firearm designed for sustained direct fire with rifle cartridges. Other automatic firearms such as automatic shotguns and automatic rifles (including assault rifles and battle rifles) ar ...

positions. 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 iron creating more of an obstacle. The NCDUs found that the best method was to blast the structural joints of a gate so that it fell down flat. The NCDU teams (designated Demolitions Gap-Assault teams) would come in at low tide to clear the obstacles. Their mission was to open sixteen wide corridors for the landing at each of the U.S. landing zones ( Omaha Beach and

Utah Beach Utah, commonly known as Utah Beach, was the code name for one of the five sectors of the Allied invasion of German-occupied France in the Normandy landings on June 6, 1944 (D-Day), during World War II. The westernmost of the five code-named la ...

). Unfortunately, the plans were not executed as laid out. The preparatory air and naval bombardment was ineffective, leaving many German guns to fire on the assault. Also, tidal conditions caused difficulties for the NCDUs. Despite heavy German fire and casualties, the NCDUs charges opened gaps in the defenses. As the infantry came ashore, some used obstacles for cover that had demolition charges on them. The greatest difficulty was on Omaha Beach. By nightfall thirteen of the planned sixteen gaps were open. Of the 175 NCDU men that landed, 31 were killed and 60 were wounded. The attack on Utah Beach was better, four dead and eleven wounded. Overall, NCDUs suffered a 53 percent casualty rate. NCDUs were also assigned to Operation Dragoon, the invasion of southern

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

, with a few units from Normandy participating there too. 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 Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its capit ...

during January 1944. A few were temporarily attached to UDTs. Later NCDUs 1–10 were combined to form Underwater Demolition Team Able. 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 During WWII

The first units designated as Underwater Demolition Teams were formed in the Pacific Theater. Rear Admiral Turner, the Navy's amphibious expert, ordered the formation of Underwater Demolition Teams in response to the assault debacle experienced at

Tarawa Tarawa is an atoll and the capital of the Republic of Kiribati,Kiribati
''

amphibious operations Amphibious warfare is a type of offensive military operation that today uses naval ships to project ground and air power onto a hostile or potentially hostile shore at a designated landing beach. Through history the operations were conducte ...

required

intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. More generally, it can be des ...

of underwater obstacles . The personnel in teams 1-15 were primarily

Seabee , colors = , mascot = Bumblebee , battles = Guadalcanal, Bougainville, Cape Gloucester, Los Negros, Guam, Peleliu, Tarawa, Kwajalein, Saipan, Tinian, Iwo Jima, Philippin ...

s that had started out in the NCDUs. UDT training was at the Waipio Amphibious Operating Base, 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. When Teams 1 and 2 were formed they were "provisional" and trained by a Marine Corps Amphibious Reconnaissance Battalion that had nothing to do with the Fort Pierce program. After a successful mission at Kwajalein, where 2 UDT men stripped down to swim trunks and effectively gathered the intelligence Admiral Turner desired. As a result of their actions the UDT mission model evolved to daylight reconnaissance, wearing swim trunks, fins, and masks. The immediate success of the UDTs made them an indispensable part of all future amphibious landings. A UDT was organized with approximately sixteen officers and eighty enlisted. One Marine and one Army officer were liaisons within each team They were deployed in every major amphibious landing after Tarawa with 34 teams eventually being commissioned. Teams 1–21 were the teams that had deployed operationally, with slightly over half of the Officers and enlisted coming from the Seabees in those teams. The remaining teams were not deployed due to the war ending.

Tarawa and the formation of UDTs

Prior to

Tarawa Tarawa is an atoll and the capital of the Republic of Kiribati,Kiribati
''

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

as an issue for

. At Tarawa the

neap tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables c ...

created draft issues for the Higgins boats (LCVPs) clearing the reef. The Amtracs carrying the first wave crossed the reef successfully. The LCVPs carrying the second wave ran aground, disembarking their Marines several hundred yards to shore in full combat gear, under heavy fire. Many drowned or were killed before making the beach, forced to wade across treacherously uneven coral. The first wave was left fighting without reinforcements and took heavy casualties on the beach. This disaster made it clear Admiral Turner that pre-assault intelligence was needed to avoid similar difficulties in future operations. To that end, Turner ordered the formation of underwater demolition teams to do

of beach conditions and do removal of submerged obstructions for Amphibious operations. After a thorough review,

found that the only people having any applicable experience with the coral were men in the Naval Construction Battalions. The Admiral tasked Lt. Thomas C. Crist (CEC) of CB 10 to develop a method for blasting coral under combat conditions and putting together a team for that purpose.The Water Is Never Cold, James Douglas O'Dell, 2000, p. 132, Brassey's, 22841 Quicksilver Drive, Dulles, Va. 20166, Lt. Crist started by recruiting others he had blasted coral with in CB 10 and by the end November 1943 he had assembled close to 30 officers and 150 enlisted men from the 7th Naval Construction Regiment, at Waipio Amphibious Operating Base on Maui.

Kwajalein and the evolution of the UDT mission model

The first operation after Tarawa was Operation Flintlock in the Marshall Islands. It began with the island of

Kwajalein Kwajalein Atoll (; Marshallese: ) is part of the Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking residents (about 1,000 mostly U.S. civil ...

in January 1944. Admiral Turner wanted the intelligence and to get it, the men that Lt. Crist had staged were used to form Underwater Demolition Teams: UDT 1 and UDT 2. Initially, the team commanders were Cmdr. E. D. Brewster (CEC) and Lt. Crist (CEC). However, Lt. Crist was made Ops officer of Team 2 and Lt. John T. Koehler was made the team Commander. As with all Seabee military training the Marines provided it. A Marine Corps Amphibious Reconnaissance Battalion oversaw five weeks further training of the Seabees in UDTs 1 and 2 to prepare for the mission. UDT 1 was tasked with two daylight recons. The men were to follow Marine Corps Recon procedure with each two-man team getting close to the beach in a

s to make their observations wearing fatigues, boots, helmets, and life-lined to their boats. Team 1 found that the

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

kept them from ascertaining conditions both in the water and on the beach as had been anticipated. 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 fatigues and boots came off.

Ensign An ensign is the national flag flown on a vessel to indicate nationality. The ensign is the largest flag, generally flown at the stern (rear) of the ship while in port. The naval ensign (also known as war ensign), used on warships, may be diffe ...

Lewis F. Luehrs and Seabee Chief Bill Acheson had anticipated that they would not be able to get the intell Admiral Turner wanted following USMC Recon protocol and had worn swim trunks beneath their fatigues. 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. 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 Luehrs and Chief Acheson made Kwajalein a developmental day in UDT history, changing both the mission model and training regimen. Luehrs would make rank and be in UDT 3 until he was made XO of UDT 18. Acheson and three other UDT officers were posted to the 301st CB as blasting officers. The 301st specialized in Harbor dredging. It saved UDT teams from blasting channels and Harbor clearance, but it required its own blasters. Admiral Turner ordered the formation of nine teams, six for VAC and three for III Amphibious Corps. Seabees made up the majority of the men in teams 1–9, 13 and 15. The officers of those teams were primarily CEC (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 most 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. In order to implement these changes and grow the UDTs, Koehler was made the commanding officer of the Naval Combat Demolition Training and Experimental Base on Maui. Admiral Turner also brought on LCDR Draper Kaufmann as a combat officer. 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 three Lt. Cmdrs were transferred from USN Beach Battalions to command UDTs 11, 12, 13 that had no background in demolition. Admiral Turner requested the establishment of the Naval Combat Demolition Training and Experimental Base at

Kihei Kihei ( haw, Kīhei, ) is a census-designated place (CDP) in Maui County, Hawaii, Maui County, Hawaii, United States. The population was 21,423 at the 2020 United States Census, 2020 census. Geography Kihei is located at (20.759122, −156.45722 ...

independent of Fort Pierce, expanding upon what had been learned from UDT 1 at Kwajalein. Operations began in February 1944 with Lt. Crist the first 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 mask Diving most often refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), ...

s, swim trunks, and a Ka-bar, creating the UDT image as "Naked Warriors" (swim-fins were added after UDT 10 introduced them).

Roi-Namur, Saipan, Tinian, and Guam

At Saipan and Tinian UDTs 5, 6, and 7 were given the missions: day time for Saipan and night for

Tinian Tinian ( or ; old Japanese name: 天仁安島, ''Tenian-shima'') is one of the three principal islands of the Commonwealth of the Northern Mariana Islands. Together with uninhabited neighboring Aguiguan, it forms Tinian Municipality, one of the ...

. 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, and 6 were the teams assigned. When it was over the Seabee-dominated teams had made

naval history Naval warfare is combat in and on the sea, the ocean, or any other battlespace involving a major body of water such as a large lake or wide river. Mankind has fought battles on the sea for more than 3,000 years. Even in the interior of large lan ...

. For the Marianas operations Admiral Turner recommended over sixty Silver Stars and over three hundred

Bronze Star The Bronze Star Medal (BSM) is a United States Armed Forces decoration awarded to members of the United States Armed Forces for either heroic achievement, heroic service, meritorious achievement, or meritorious service in a combat zone. Wh ...

s with Vs for UDTs 3–7 That was unprecedented in U.S. Naval/Marine Corps history. For UDTs 5 and 7, all officers received silver stars and all the enlisted received bronze stars with Vs for Operation Forager (Tinian).Naked Warriors, Cdr. Francis Douglas Fane USNR (Ret.), St. Martin's Press, 175 Fifth Ave, New York, NY 10010, 1996, pp. 122, 131, For UDTs 3 and 4 all officers received a silver stars and all the enlisted received bronze stars with Vs for Operation Forager (Guam). Admiral Conolly felt the commanders of teams 3 and 4 (Lt. Crist and Lt. W.G. Carberry) should have received Navy Crosses. Teams 4 & 7 also received Naval Unit Commendations.

Peleliu, Philippines, and Iwo Jima

UDTs 6, 7, and 10 drew the

Peleliu Peleliu (or Beliliou) is an island in the island nation of Palau. Peleliu, along with two small islands to its northeast, forms one of the sixteen states of Palau. The island is notable as the location of the Battle of Peleliu in World War II. H ...

assignment while UDT 8 went to

Angaur , or in Palauan, is an island and state in the island nation of Palau. History Angaur was traditionally divided among some eight clans. Traditional features within clan areas represent important symbols giving identity to families, clans an ...

. The officers were almost all CEC and the enlisted were Seabees. 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.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, 8 August 2017, National Park Service, 1100 Ohio Drive, SW, Washington, DC 2024

/ref> but, the OSS was not allowed to operate in the Asiatic-Pacific Theater, 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 Swimfins, swim fins, diving fins, or flippers are finlike accessories worn on the feet, legs or hands and made from rubber, plastic, carbon fiber or combinations of these materials, to aid movement through the water in water sports activities s ...

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 its CO and XO were CEC and some of Team Able was incorporated. In the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

Leyte Gulf UDTs 10 & 15 reconnoitered beaches at

Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as ...

, 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. 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. There were classes in night operations, unit control, coral and lava blasting in addition to bivouacking, small unit tactics and small arms. Lt Crist would be promoted to Lt Cmdr and the team would remain in Hawaii until April 1945. At that time the Seabees of UDT 3 were transferred to Fort Pierce to be the instructors there. In all they would train teams 12 to 22. 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 than the UDTs with the skipper of one boat earning a

Medal of Honor The Medal of Honor (MOH) is the United States Armed Forces' highest military decoration and is awarded to recognize American soldiers, sailors, marines, airmen, guardians and coast guardsmen who have distinguished themselves by acts of valo ...

. The next day a Japanese bomb hit UDT 15's APD, 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.UDT 13, The Men From Fort Pierce(excerpts), Marvin Cooper, U. S. Naval Special Warfare Archives web-sit

/ref> Lt Cmdr. Vincent Moranz of UDT 13 was "reluctant, and radioed that his men ... were not salvage-men. It is reported that Capt. (Bull) Hanlon, Underwater Demolition Operations Commanding Officer radioed back that he did not want anything salvaged, he wanted that beach cleared." The difference 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 the Navy gave them different unit awards: UDT 12 a Presidential Unit Citation (United States), 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 a 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 Enewetak Atoll (; also spelled Eniwetok Atoll or sometimes Eniewetok; mh, Ānewetak, , or , ; known to the Japanese as Brown Atoll or Brown Island; ja, ブラウン環礁) is a large coral atoll of 40 islands in the Pacific Ocean and with i ...

Ulithi Ulithi ( yap, Wulthiy, , or ) is an atoll in the Caroline Islands of the western Pacific Ocean, about east of Yap. Overview Ulithi consists of 40 islets totaling , surrounding a lagoon about long and up to wide—at one of the larges ...

Leyte Leyte ( ) is an island in the Visayas group of islands in the Philippines. It is eighth-largest and sixth-most populous island in the Philippines, with a total population of 2,626,970 as of 2020 census. Since the accessibility of land has be ...

, Lingayen Gulf,

Zambales Zambales, officially the Province of Zambales ( fil, Lalawigan ng Zambales; ilo, Probinsia ti Zambales; Pangasinan: ''Luyag/Probinsia na Zambales''; xsb, Probinsya nin Zambales), is a province in the Philippines located in the Central Luzon re ...

Labuan Labuan (), officially the Federal Territory of Labuan ( ms, Wilayah Persekutuan Labuan), is a Federal Territory of Malaysia. Its territory includes and six smaller islands, off the coast of the state of Sabah in East Malaysia. Labuan's capita ...

, and

Brunei Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...

Bay. At Lingayen UDT 9 was aboard the USS Belknap when she was hit by a

Kamikaze , officially , were a part of the Japanese Special Attack Units of military aviators who flew suicide attacks for the Empire of Japan against Allied naval vessels in the closing stages of the Pacific campaign of World War II, intending t ...

. It cost the team one officer, 7 enlisted, 3

MIA Mia, MIA, or M.I.A. may refer to: Music Artists * M.I.A. (rapper) (born 1975), English rapper and singer * M.I.A. (band), 1980s punk rock band from Orange County, California * MIA., a German rock/pop band formed in 1997 * Mia (singer) (born 1983) ...

and 13 wounded.

Okinawa to the end of the war

The largest UDT operation of WWII was the invasion of

Okinawa is a prefecture of Japan. Okinawa Prefecture is the southernmost and westernmost prefecture of Japan, has a population of 1,457,162 (as of 2 February 2020) and a geographic area of 2,281 km2 (880 sq mi). Naha is the capital and largest city ...

, 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 Hypothermia is defined as a body core temperature below in humans. Symptoms depend on the temperature. In mild hypothermia, there is shivering and mental confusion. In moderate hypothermia, shivering stops and confusion increases. In severe ...

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. By war's 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. 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 A frogman is someone who is trained in scuba diving or swimming underwater in a tactical capacity that includes military, and in some European countries, police work. Such personnel are also known by the more formal names of combat diver, comb ...

" but rather "Demolitioneers" which had carried over from the NCDUs 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 Balikpapan is a seaport city in East Kalimantan, Indonesia. Located on the east coast of the island of Borneo, the city is the financial center of Kalimantan. Balikpapan is the city with the largest economy in Kalimantan with an estimated ...

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...

. The UDTs continued to prepare for the invasion of Japan until

VJ Day Victory over Japan Day (also known as V-J Day, Victory in the Pacific Day, or V-P Day) is the day on which Imperial Japan surrendered in World War II, in effect bringing the war to an end. The term has been applied to both of the days on ...

when the need for their services ceased. With the draw-down from the war two half-strength UDTs were retained, one on each coast: UDT Baker and UDT Easy. However, the UDTs were the only special troops that avoided complete disbandment after the war, unlike the OSS Maritime Unit, the VAC Recon Battalion, and several Marine recon missions. In 1942 the Seabees became a completely new branch of the United States War Department. The Marine Corps provided both training and an organizational model. Something that either was not shared or the Seabees chose to ignore or considered not important was the keeping of logs, journals and records. The Seabees brought this record keeping approach with to the NCDUs and UDTs.

After World War II

Japan occupation

On 20 August 1945 embarked UDT 21 at Guam as a component of the U.S. occupation force heading for Japan. 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 is a bay located in the southern Kantō region of Japan, and spans the coasts of Tokyo, Kanagawa Prefecture, and Chiba Prefecture. Tokyo Bay is connected to the Pacific Ocean by the Uraga Channel. The Tokyo Bay region is both the most populous ...

. Their assessment was that the area was well suited for landing U.S. amphibious forces. UDT 21 made a large sign to greet the Marines on the beach. Team 21 was all fleet and the sign said greetings from "USN" UDT 21. The next day ''Begor'' took UDT 21 to Yokosuka Naval Base. There the team cleared the docks for the first U.S. warship to dock in Japan, . The team remained in Tokyo Bay until 8 Sept when it was tasked with locating remaining

and two-man submarines at Katsura Wan, Uchiura Wan at Suruga Bay, Sendai, Onohama Shipyards and Choshi.USS BEGOR (APD-127) veterans webpage
/ref> Orders arrived for ''Begor'' to return the team to San Diego on 27 September. From 21 to 26 September UDT 11 was at Nagasaki and reported men getting sick from the stench.

China

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 Operation Beleaguer was a major United States military operation led by Maj. Gen. Keller E. Rockey. He commanded 50,000 men of the III Marine Amphibious Corps that deployed to northeastern China's Hopeh (Hebei, 河北) and Shantung (Shandong, ...

to recon the landings of the

1st Marine Division The 1st Marine Division (1st MARDIV) is a Marine division of the United States Marine Corps headquartered at Marine Corps Base Camp Pendleton, California. It is the ground combat element of the I Marine Expeditionary Force (I MEF). It is th ...

at Taku and

Tsingtao Qingdao (, also spelled Tsingtao; , Mandarin: ) is a major city in eastern Shandong Province. The city's name in Chinese characters literally means " azure island". Located on China's Yellow Sea coast, it is a major nodal city of the One Belt ...

the first two weeks of October 1945.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-sit

/ref> On their way to China the Navy had UDT 8 carry out a mission at Jinaen,

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

8–27 September 1945. When UDT 9 arrived back in the States it was made one of the two post-War teams and redesignated UDT Baker. UDT 8 was also sent to China and was at Taku,

Chefoo Yantai, formerly known as Chefoo, is a coastal prefecture-level city on the Shandong Peninsula in northeastern Shandong province of People's Republic of China. Lying on the southern coast of the Bohai Strait, Yantai borders Qingdao on the ...

, and Tsingtao.

Operation Crossroads

Bikini atoll Bikini Atoll ( or ; Marshallese: , , meaning "coconut place"), sometimes known as Eschscholtz Atoll between the 1800s and 1946 is a coral reef in the Marshall Islands consisting of 23 islands surrounding a central lagoon. After the Seco ...

was chosen for the site of the

nuclear tests Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detonations are affected by ...

Operation Crossroads Operation Crossroads was a pair of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity in July 1945, and the first detonations of nuclear devices since the ...

"In March 1946,
Project Y The Los Alamos Laboratory, also known as Project Y, was a secret laboratory established by the Manhattan Project and operated by the University of California during World War II. Its mission was to design and build the first atomic bombs. Ro ...
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".Operations Crossroads, DNA 6032F, prepared by the Defense Nuclear Agency, p.189-90
/ref>

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 USS ''Begor'' (DE-711/APD-127) was a of the United States Navy. Namesake Fay Broughton Begor was born on 15 October 1916 in Moriah, New York state. He earned a bachelor’s degree from Union College, Schenectady, New York, in June 1937. Earnin ...

at the Seabee base Port Hueneme, CA, 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.USS BEGOR (APD-127) Veterans webpage
/ref> ''Begor'' came to have the reputation as the most contaminated boat in the fleet. A major issue afterwards was the treatment of the dislocated natives. In November 1948, the Bikinians were relocated to the uninhabited Island of

Kili KILI (90.1 FM), licensed to Porcupine, South Dakota, is a non-profit radio station broadcasting to the Lakota people on the Pine Ridge, Cheyenne River, and Rosebud Indian Reservations, part of the Great Sioux Nation. The station started broadc ...

, however that island was located inside a

coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. C ...

that had no channel for access to the sea. In the spring of 1949, the Governor of the Trust Territories, Marshall Group requested the U.S. Navy blast a channel to change this. That task was given to the Seabees on Kwajalin whose CO quickly determined this was actually a UDT project. He sent a request to CINCPACFLT who forwarded it to COMPHIBPAC. This ultimately resulted in the sending of UDT 3 on a

Civic action program A civic action program also known as civic action project is a type of operation designed to assist an area by using the capabilities and resources of a military force or civilian organization to conduct long-term programs or short-term projects. ...

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.U.S. Naval Special Warfare Archives, After Operation Crossroads – Kili Island, Mack M. Boynton, December 21, 2013
/ref>

Submersible Operations

Post WWII 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 LtCmdr. Kauffman, but was told the device was not applicable to current UDT operations. 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 A coast guard or coastguard is a maritime security organization of a particular country. The term embraces wide range of responsibilities in different countries, from being a heavily armed military force with customs and security duties to ...

, and the UDTs. In 1947, he demonstrated the LARU to LtCmdr. Francis "Doug" Fane, then a senior UDT commander. LtCmdr. 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, LtCmdr. Fane invited Dr. Lambertsen to NAB Little Creek,

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

in January 1948 to demonstrate and train UDT personnel in SCUBA operations. This was the first-ever SCUBA training for USN divers. Following this training, Lcdr. Fane and Dr. Lambertsen demonstrated new UDT capabilities with a successful lock-out and re-entry from , an underway submarine, to show the Navy's need for this capability. LtCmdr. 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) Lieutenant junior grade is a junior commissioned officer rank used in a number of navies. United States Lieutenant (junior grade), commonly abbreviated as LTJG or, historically, Lt. (j.g.) (as well as variants of both abbreviations), ...

Bruce Dunning. LtCmdr. 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 UDTs, led by LtCmdr. Fane, established training facilities at Saint Thomas in the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rico Trench and St. Cro ...

. The UDTs also began developing weapons skills and procedures for

commando Royal Marines from 40 Commando on patrol in the Sangin">40_Commando.html" ;"title="Royal Marines from 40 Commando">Royal Marines from 40 Commando on patrol in the Sangin area of Afghanistan are pictured A commando is a combatant, or operativ ...

operations on land in coastal regions. The UDTs started experiments with insertion/extraction by helicopter, jumping from a moving helicopter into the water or rappelling like

mountain climber Mountaineering or alpinism, is a set of outdoor activities that involves ascending tall mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas. Indoor climbing, sport climbing, an ...

s 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 The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built by Lockheed Corporation, Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the 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. Training this technique was discontinued following the death of a SEAL at NAB Coronado during a training exercise. Teams still utilize the Skyhook for equipment extraction and retain the combat capability for personnel if needed.

Korean War

During the

Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...

, the UDTs operated on the coasts of

North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korean Peninsula and shares borders with China and Russia to the north, at the Yalu (Amnok) and T ...

, with their efforts initially focused on demolitions and mine disposal. Additionally, the UDT accompanied

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. Its western border is formed by the Yellow Sea, while its eas ...

n commandos on raids in the North to demolish

railroad Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are incorporated in tracks. In contrast to road transport, where the vehicles run on a pre ...

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 Battle of Incheon (), also spelled Battle of Inchon, was an amphibious invasion and a battle of the Korean War that resulted in a decisive victory and strategic reversal in favor of the United Nations Command (UN). The operation involved s ...

, the amphibious landing at

Inchon Incheon (; ; or Inch'ŏn; literally "kind river"), formerly Jemulpo or Chemulp'o (제물포) until the period after 1910, officially the Incheon Metropolitan City (인천광역시, 仁川廣域市), is a city located in northwestern South Kore ...

. 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 Wŏnsan (), previously known as Wŏnsanjin (), Port Lazarev, and Genzan (), is a port city and naval base located in Kangwŏn Province, North Korea, along the eastern side of the Korean Peninsula, on the Sea of Japan and the provincial capital. ...

harbor, under fire from enemy shore batteries. Two minesweepers were sunk in these operations. A UDT diver dove on the wreck of USS Pledge (AM-277), 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 Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

SH-3A Sea King HS-6 practicing Mercury space capsule recovery 1963

NASA

UDT-12 divers at the Apollo 8 capsule 1968

Initially, the splashdown of U.S. manned space capsules were unassisted.UDTs and the Space Flight Programs, UDT Navy Seal Museum Archives website, Fort Pierce, F

/ref> That changed quickly after the second manned flight. When Mercury 11 hit the water the hatch blew and she sank nearly drowning

Gus Grissom Virgil Ivan "Gus" Grissom (April 3, 1926 – January 27, 1967) was an American engineer, pilot in the United States Air Force, and member of the Mercury Seven selected by National Aeronautics and Space Administration's (NASA) as Project Mercur ...

. After that all Mercury, Gemini, and Apollo space capsules were met by UDTs 11 or 12 upon splashdown. Before the hatch was opened the UDTs would attach a flotation collar to the capsule and

liferaft A lifeboat or liferaft is a small, rigid or inflatable boat carried for emergency evacuation in the event of a disaster aboard a ship. Lifeboat drills are required by law on larger commercial ships. Rafts ( liferafts) are also used. In the m ...

for the

astronauts An astronaut (from the Ancient Greek (), meaning 'star', and (), meaning 'sailor') is a person trained, equipped, and deployed by a human spaceflight program to serve as a commander or crew member aboard a spacecraft. Although generally r ...

to safely exit the craft.

Vietnam War

330-PSA-51-65 (USN 1109964F) (22527274968)

The Navy entered the

in 1958, when the UDTs delivered a small watercraft far up the

Mekong River The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's twelfth longest river and the third longest in Asia. Its estimated length is , and it drains an area of , discharging of water annual ...

into Laos. In 1961, naval advisers started training South Vietnamese personnel in South Vietnam. The men were called the ''Liên Đoàn Người Nhái'' (LDNN) or Vietnamese Frogmen, which translates as "Frogmen Team". UDT teams carried out hydrographic surveys in South Vietnam's coastal waters and reconnaissance missions of harbors, beaches and rivers often under hazardous conditions and enemy fire. 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's Beak and French canal AO's through I Corps and the Song Cui Dai estuary south of Da Nang.

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 Unconventional warfare (UW) is broadly defined as "military and quasi-military operations other than conventional warfare" and may use covert forces, subversion, or guerrilla warfare. This is typically done to avoid escalation into conventional ...

", 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 The United States Navy Sea, Air, and Land (SEAL) Teams, commonly known as Navy SEALs, are the U.S. Navy's primary special operations force and a component of the Naval Special Warfare Command. Among the SEALs' main functions are conducting sm ...

, an acronym for Sea, Air, and Land. Initially there was a lag in the unit's creation until President

John F. Kennedy John Fitzgerald Kennedy (May 29, 1917 – November 22, 1963), often referred to by his initials JFK and the nickname Jack, was an American politician who served as the 35th president of the United States from 1961 until his assassination ...

took office. Kennedy recognized the need for unconventional warfare, and supported the use of

special operations Special operations (S.O.) are military activities conducted, according to NATO, by "specially designated, organized, selected, trained, and equipped forces using unconventional techniques and modes of employment". Special operations may include ...

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 Manuel Antonio Noriega Moreno (; February 11, 1934 – May 29, 2017) was a Panamanian dictator, politician and military officer who was the ''de facto'' ruler of Panama from 1983 to 1989. An authoritarian ruler who amassed a personal f ...

and Colombian drug lord Pablo Escobar, and playing integral roles in the wars in Iraq and Afghanistan.

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.

Unit awards

The UDTs have received several

unit citation A unit citation is a formal, honorary mention by high authority of a military unit's specific and outstanding performance, notably in battle. Similar mentions can also be made for individual soldiers. Alternatively or concurrently, the unit can be ...

s 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 The United States Armed Forces awards and decorations are primarily the medals, service ribbons, and specific badges which recognize military service and personal accomplishments while a member of the U.S. Armed Forces. Such awards are a means ...

have different categories, (i.e. Service, Campaign, Unit, and Personal). Unit Citations are distinct from the other decorations. Naval Combat Demolition Force O (Omaha beach) Normandy * United States Navy Presidential Unit Citation ribbon

United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation Normandy Naval Combat Demolition Force U (Utah beach) : Normandy * Navy Unit Commendation ribbon

Navy Unit Commendation : Normandy UDT 1 * Navy Unit Commendation ribbon

Navy Unit Commendation : KoreaNaval History and Heritage Command website, Part 2 – Unit Awards, Published:Mon Aug 31 14:01:11 EDT 2015, p. 22
/ref> UDT 4 * Navy Unit Commendation ribbon

Navy Unit Commendation : Guam * Navy Unit Commendation ribbon

Navy Unit Commendation : Leyte * Navy Unit Commendation ribbon

Navy Unit Commendation : Okinawa UDT 7 * Navy Unit Commendation ribbon

Navy Unit Commendation : Marianas * Navy Unit Commendation ribbon

Navy Unit Commendation : Western Carolinas UDT 11 * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : Okinawa.US Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
/ref> * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : Bruni Bay, Borneo, * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : Balikpapan, Burneo, * Navy Unit Commendation ribbon

Navy Unit Commendation 1966 *

Navy Meritorious Unit Commendation ribbon

Navy Meritorious Unit Commendation The Meritorious Unit Commendation (MUC; pronounced ''muck'') is a mid-level unit award of the United States Armed Forces. The U.S. Army awards units the Army MUC for exceptionally meritorious conduct in performance of outstanding achievement or s ...

1968 *

Navy Unit Commendation 1969 * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : 1969 *

1969 *

1970 *

Republic of Vietnam

Civil Actions Medal The Republic of Vietnam Civil Actions Medal ( vi, Dân-Vụ Bội-Tinh) also known as the Vietnam Civil Actions Medal or Civil Actions Medal, is a military decoration of the former South Vietnamese government (1955–75). The medal was created ...

Unit Citation * Vietnam gallantry cross unit award-3d

Republic of Vietnam Gallantry Cross with Palm Unit Award *

Coast Guard Meritorious Unit Commendation ribbon

Coast Guard Meritorious Unit Commendation UDT 12 * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : Iwo Jima, * United States Navy Presidential Unit Citation ribbon

Presidential Unit Citation : Okimawa * Navy Unit Commendation ribbon

Navy Unit Commendation 1966 *

Vietnam 1967 *

Vietnam 1968 *

Vietnam 1969 * Vietnam gallantry cross unit award-3d

Republic of Vietnam Gallantry Cross with Palm Unit Award * Armed Forces Expeditionary Medal ribbon

Operation Eagle Pull Operation Eagle Pull was the United States military evacuation by air of Phnom Penh, Cambodia, on 12 April 1975. At the beginning of April 1975, Phnom Penh, one of the last remaining strongholds of the Khmer Republic, was surrounded by the Khmer ...

Operation Frequent Wind Operation Frequent Wind was the final phase in the evacuation of American civilians and "at-risk" Vietnamese from Saigon, South Vietnam, before the takeover of the city by the North Vietnamese People's Army of Vietnam (PAVN) in the Fall of Saig ...

Humanitarian Service Medal 1979

Boat People Vietnamese boat people ( vi, Thuyền nhân Việt Nam), also known simply as boat people, refers to the refugees who fled Vietnam by boat and ship following the end of the Vietnam War in 1975. This migration and humanitarian crisis was at its h ...

UDT 13 *

VietnamUS Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
/ref> 1969 * Vietnam gallantry cross unit award-3d

Republic of Vietnam Gallantry Cross with Palm Unit Award 1970 UDT 14 * Navy Unit Commendation ribbon

Navy Unit Commendation : Luzon * Navy Unit Commendation ribbon

Navy Unit Commendation : Iwo Jima * Navy Unit Commendation ribbon

Navy Unit Commendation : Okinawa UDT 21 * Navy Expeditionary Medal ribbon

Navy Expeditionary Medal The Navy Expeditionary Medal is a military award of the United States Navy which was established in August 1936. Award criteria The General Orders of the Department of the Navy which established the medal states, "The medal will be awarded, to ...

VietnamUS Navy Awards, Chief of Naval Operations, 2000 Navy Pentagon, Washington, D.C. 20350
/ref> *

Vietnam *

Vietnam UDT 22 *

Vietnam 1969 *OPNAV NOTICE 1650, MASTER LIST OF UNIT AWARDS AND CAMPAIGN MEDALSOPNAV NOTICE 1650, MASTER LIST OF UNIT AWARDS AND CAMPAIGN MEDALS, DEPARTMENT OF THE NAVY, OFFICE OF THE CHIEF OF NAVAL OPERATIONS, 2000 NAVY PENTAGON, WASHINGTON, DC 20350-2000, 18 September 2002
/ref>

Fiction

* '' The Frogmen'' (1951), starring

Dana Andrews Carver Dana Andrews (January 1, 1909 – December 17, 1992) was an American film actor who became a major star in what is now known as film noir. A leading man during the 1940s, he continued acting in less prestigious roles and character parts ...

and

Richard Widmark Richard Weedt Widmark (December 26, 1914March 24, 2008) was an American film, stage, and television actor and producer. He was nominated for an Academy Award for his role as the villainous Tommy Udo in his debut film, ''Kiss of Death'' (1947) ...

. World War II film based on the Underwater Demolition Teams. Contemporary UDT members appear in several sequences. * '' Underwater Warrior'' (1958) directed by

Andrew Marton Andrew Marton (born Endre Marton; 26 January 1904 – 7 January 1992) was a Hungarian-American film director. In his career, he directed 39 films and television programs, and worked on 16 as a second unit director, including the chariot race in ...

is based on the memoirs of Lieutenant-Commander Francis Douglas Fane, ''Naked Warriors''.

References

External links

Navy UDT-SEAL Museum

Pritzker Military Museum & Library

"TNT Divers"
''Popular Mechanics'', November 1945, pp. 72–73, one of earliest articles on WW2 UDT units. {{Underwater diving, prodiv Military engineering Armed forces diving Special operations units and formations of the United States Navy Frogman operations