UDTs were pioneers in underwater demolition, closed-circuit diving, combat swimming, riverine warfare and midget submarine (dry and wet submersible) operations.

[3] The United States Navy studied the problems encountered by the disastrous Allied amphibious landings during the Gallipoli Campaign of World War I.

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.

[2] 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.

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.

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 gunners inflicting heavy U.S.

[2] After that experience, Rear Admiral Kelley Turner, Commander of the V Amphibious Corps (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 Regiment[4] at Waipio Amphibious Operating Base on Oahu to form the nucleus of a reconnaissance and demolition training program.

[citation needed] 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.

[10] Also in May, the Navy created Naval Combat Demolition Units (NCDUs) tasked with eliminating beach obstructions in advance of amphibious assaults, going ashore in an LCRS inflatable boat.

[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 NCDUs: 11, 22–30, 41–46, 127–8, 130–42[15] The Germans had constructed elaborate defenses on the French coast.

Rear Admiral Turner, the Navy's amphibious expert, ordered the formation of Underwater Demolition Teams in response to the assault debacle experienced at Tarawa.

[citation needed] 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.

The LCVPs carrying the second wave ran aground, disembarking their Marines several hundred yards to shore in full combat gear, under heavy fire.

To that end, Turner ordered the formation of underwater demolition teams to do reconnaissance of beach conditions and do removal of submerged obstructions for Amphibious operations.

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.

[19] 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,[4] at Waipio Amphibious Operating Base on Maui.

Ensign Lewis F. Luehrs and Seabee Chief Bill Acheson had anticipated that they would not be able to get the intel Admiral Turner wanted following USMC Recon protocol and had worn swim trunks beneath their fatigues.

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.

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.

[citation needed] Admiral Turner requested the establishment of the Naval Combat Demolition Training and Experimental Base at Kihei independent of Fort Pierce, expanding upon what had been learned from UDT 1 at Kwajalein.

[33] 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.

"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".

On 27 April, 7 officers and 51 enlisted men embarked the USS Begor at the Seabee base Port Hueneme, CA,[37] for transit to Bikini.

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.

[47] That changed quickly after the second crewed flight; when Mercury 11 hit the water following reentry, the hatch blew and she sank, nearly drowning Gus Grissom.

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.

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.

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.