The Underwater Demolition Teams of the Pacific

By: Mark Loproto

During the First World War, the Allies suffered great losses due to catastrophic amphibious landings, notably during the Gallipoli Campaign. The US military is always eager to learn from past mistakes, and so these landings were scrutinized in the years that followed. The mid-1930s saw testing of new landing techniques. These experiments and attempts at devising new techniques continued well into the Second World War, when the United States started to realize it was going to need to perfect amphibious landings to effectively combat its enemies.

Admiral Kelly Turner, creator of the Underwater Demolition Teams

Admiral Kelly Turner, creator of the Underwater Demolition Teams

The importance of this came into sharp focus during the Battle of Tarawa in November, 1943. Several Naval amphibious landing craft struck the coral reef, which had been surveyed via aerial reconnaissance and deemed deep enough to allow for the craft to pass. When casualties were sustained because of the incident, Admiral Kelly Turner, Commander of the 5th Amphibious Force, ordered 180 men to Waimanalo Amphibious Training Base on Oahu for specialized training.

These men would become the seeds of the Underwater Demolition Teams (UDT) of the Pacific.

With Japan steadily taking over islands throughout the Pacific, the Allies were forced to make many amphibious landings. To minimize casualties and damage done to naval vessels, the Underwater Demolition Teams were quickly developed and deployed.





The Underwater Demolition Teams of the Pacific

Underwater Demolition Teams have carried out many missions since they were first made active on August 15, 1942, and they saw plenty of action during the remaining three years of World War II.

UDTs were tasked with completing full sweeps of the beaches and waters off an island’s coast. The purpose of these missions was to determine if there was anything, man-made or naturally-occurring, that would impede the arrival of landing craft. If they encountered any underwater obstacles, it was their task to demolish them.

Under the order of Admiral Turner, nine Underwater Demolition Teams were initially formed, made up primarily of Seabees. Training was extensive and utilized all of the tools deemed necessary to ensure unobstructed landings. Inflatable boats were utilized as the men needed to be able to paddle quickly into shallow waters. After training, the UDTs were deployed in the Pacific. From their first deployment, Underwater Demolition Teams were used in every major amphibious landing in the War in the Pacific.

The following were among the most notable deployments of Underwater Demolition Teams.


UDT members on Ulithi, 1945

UDT members on Ulithi, 1945

After the disaster at Tarawa, Admiral Turner feared a repeat incident at Kwajalein, in the Marshall Islands. A reconnaissance at night would put the team at risk of running aground on coral or falling victim to traps laid out by the Japanese. Therefore, UDT 1 performed two daylight recons of the area. The team approached Kwajalein in a rubber boat, but the coral prevented the unit from getting close enough to the shore to ascertain beach conditions. As it was a vital part of their task in ensuring there were no traps laid out by Japan, two Seabees, Ensign Lewis F Luehrs and Chief Bill Acheson, stripped down to bathing suits they had worn under their fatigues and swam across the reef.

Despite the enormous risk, the two remained undetected and were able to fully scope out the shore. They presented their findings—still in their swim trunks—directly to Admiral Turner.

The recon of Kwajalein was a turning point for the Underwater Demolition Teams as Turner determined that swimming was going to be an important element of shore reconnaissance. From then on, members of the UDTs were trained to be strong swimmers. While UDT 1 wore fatigues and full gear, future UDTs would be outfitted with swim trunks, diving masks, and fins. This new appearance earned them the nickname “Naked Warriors.”

Peleliu, the Philippines, Guam, and Iwo Jima

US Marines landing on Iwo Jima

US Marines landing on Iwo Jima

In the wake of Kwajalein and after implementing new training and equipment, Underwater Demolition Teams had a hand in planning landings at Peleliu, Guam, the Philippines, and Iwo Jima. While many UDT missions went off without a hitch, the initial recon of Iwo Jima’s beaches resulted in one man wounded. UDT 15, serving aboard USS Blessman (APD-48), also suffered casualties when a Japanese bomber attacked. Fifteen men were killed and 23 were injured, resulting in the largest loss of life suffered by the UDT unit.

When it came time to prepare for Iwo Jima, the UDTs were able to successfully recon the area and clear the beaches of damaged craft. The versatile team cleared the beach of debris, allowing space for the landing parties to disembark.



The invasion of Okinawa was a major action of the War in the Pacific and planning for it required the largest UDT operation to date. UDTs 7, 11, 12, 13, 14, 16, 17, and 18 —nearly 1,000 men—were summoned to take stock of Okinawa’s shorelines.

Swimming in waters that threatened hypothermia, the men cleared debris and Japanese traps like pointed poles embedded in the coral reef. UDT 16 suffered the loss of one man and did not complete its operation. UDT 11 returned the following the day to finish the job.

Post-World War II

Naked Warrior statue, National Navy SEAL Museum

Naked Warrior statue, National Navy SEAL Museum

With the need for Underwater Demolition Teams diminished, after World War II, the number of teams was reduced by half. The teams continued to train and enhance their shallow-water operations, integrating SCUBA equipment along the way. UDTs saw action during the Korea and Vietnam conflicts.

The Underwater Demolition Teams would become known as the forerunners of the US Navy SEALS.

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