graduate

Underwater Demolition Teams


Photograph of UDT frogman

U.S. Navy. Via ibiblio.org

Underwater demolition teams (UDTs) were first organized in the Pacific following the Tarawa invasion, when failure to anticipate the difficulty of crossing the reef to the invasion beaches led to heavy casualties. Each team consisted of 15 officers and 75 men, mostly selected from Navy construction and engineering units, but with a few members of Naval Combat Demolition Teams that had been training for the Normandy invasion in Europe. Initially two teams were organized, but by the end of the war their number would increase to 34. They first saw combat in the Marshalls invasion in January 1944.

UDTs were tasked with clearing the way for landing craft. This entailed neutralizing mines and landing obstacles and clearing channels through reefs. Surprisingly, training initially emphasized the use of rubber rafts and avoiding the need to enter the water.  It was quickly discovered that men wearing helmets and full battle dress paddling rubber rafts could not get close enough to shore for a thorough reconnaissance. As a consequence, Naval Combat Swimming was added to the tactics and training of the UDTs, and a candidate had to be capable of swimming two miles to qualify. Team members became expert at swimming wearing only face masks, swim trunks, and shoes. This worked well so long as the UDTs were operating in warm southern waters, but as the American offensive moved north towards Japan, the UDTs faced the challenge of operating in cold water where there was danger of hypothermia and severe cramps. The use of wet suits was not introduced until long after the war ended. 

UDTs were typically transported to the objective on destroyer-transports, each of which could carry one or two teams. The frogmen would then transfer to their rubber boats for the final approach to the beach.

The principal equipment of the UDTs was 20-pound rubber tubes of tetryl explosive that could be easily emplaced around obstacles for demolition. The UDTs also used blocks of tetryl wound with primer cord and soft wire and carried in a "Schantz pack", a kind of fabric apron with flotation bladders and four pockets for charges. Charges were attached using the metal wire and the primer cord was run to a main trunk leading to the fuse. Each charge was capable of bringing down a wooden post a foot in diameter.

Although the main mission of UDTs was clearing obstacles with explosives, they had an important secondary mission of scouting enemy positions close to shore. UDTs returning from a mission were immediately debriefed by intelligence officers, who then passed the information to landing force commanders. Because sufficiently effective reconnaissance could not be carried out at night, the UDTs operated in daylight under cover of 40mm fire from LCI gunboats. Team members painted rings on their bodies at one foot (30 cm) intervals to help estimate water depth, and they carried a stylus and plastic square to make waterproof notes.

Postwar most of the UDTs were disbanded, leaving just two on each coast. These became the ancestors of today's Navy SEALs.

References

Morison (1953)
National Navy UDT-SEAL Museum (accessed 2008-1-19)

Smith (1966)


Valid HTML 4.01 Transitional