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Combat Demolition Units And UDTs

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The invasion of Tarawa Atoll in late 1943 turned out to be a watershed event in the history of naval special warfare. The operation would remain well known to the Marine Corps and the Navy who took part in its execution. The name "Terrible Tarawa" was remembered through World War II and for some years afterward.

Rear Admiral Richmond Kelly Turner was in overall command of Operation GALVANIC, the invasion of the Gilbert Islands, including Tarawa Atoll. The taking of the Gilberts was planned to be one of the major openings of the Central Pacific campaign against the Japanese. General Douglas MacArthur would conduct his campaign against the Japanese up through New Guinea and the Philippines. The other point of the Allied two-pronged offensive against the Japanese would start with the Operation GALVANIC action. The emphasis on the Central Pacific holding the first major action was placed on Galvanic by the U.S. Joint Chiefs of Staff and the CNO, Admiral King.

Planning for the invasion of Tarawa was based on a number of intelligence sources, including charts, photographs, surveys, and the interrogation of people who were familiar with the area from prewar times. Aerial photographs of Tarawa were taken in September and October 1943. In addition, the submarine USS Nautilus conducted surveys of the offshore waters and beach emplacements at Tarawa in late September and early October. These studies filled in a host of missing hydrographic data on the offshore waters at Tarawa. Photographs taken through the submarine's periscope also showed the beaches in great detail.

Plans were made to land the initial waves of troops on Tarawa from tracked amphibious vehicles (LVTs). The limited number of the amphibious vehicles available would require that the follow-up troops be landed in LCVPs. Landings at Makin Atoll in the Gilberts were timed to take place simultaneously with the Tarawa actions.

On 20 November 1943, the landings on Betio, the main island of the Tarawa Atoll began. The first waves of LVTs faced heavy fire from the many Japanese fortifications that survived the preinvasion bombardment. The follow-up waves of LCVPs found a much worse problem than enemy fire. The reefs around Tarawa were covered by much less water than was planned for. An unusual tidal condition left many of the reefs with water far too shallow for the landing craft to cross.

Landing craft ran aground far from the shores of Betio Island. Heavily laden assault troops had to wade in to shore, sometimes hundreds of yards away, in the face of heavy enemy fire. More Marines drowned in the waters off Tarawa during the landings than were killed by enemy fire taking the island itself in over three days of combat. Admiral Turner swore that the mistakes that led to Tarawa earning the nickname "Terrible Tarawa" would not be repeated.

BEACH JUMPERS In warfare, deception has always been as valuable a weapon as a firearm, vehicle, or ship. A specialized naval deception unit was founded during World War II based on an idea of a man who was well versed in the art of illusions. That man was the actor Douglas Fairbanks Jr., then a Navy lieutenant, and the unit he proposed would become the Navy Beach Jumpers. The Beach Jumpers were an elite unit that used modern sound effects, electronics, and other tricks to make a group of small craft appear to be a much larger task force. These Beach Jumper units were first used as part of Operation HUSKY, the invasion of Sicily, in July 1943. The German forces were convinced that they had detected and repulsed an Allied landing force. Instead, a Beach Jumper unit had fooled them into directing some of their limited assets to an area that wasn't threatened with a landing. The Beach Jumpers are among the most unconventional units that ever were active in combat. Though not used for the Normandy invasions, the Beach Jumpers proved their worth in other actions during World War II. After the war, they were retained in the Navy. Eventually, the Beach Jumpers were assigned to the same organizational command as another Navy unconventional warfare unit, the UDTs and later the SEAL Teams.

The Creation of the UDTs

In the first week of November 1943, just prior to Operation GALVANIC and the invasion of Tarawa, the Fifth Amphibious Force, under Real Admiral Turner, was directed to begin the organization and specialized training of demolition personnel. The training was to be such that the demolition specialists would be able to clear natural coral formation obstacles as well as man-made obstacles and mines from future invasion beaches. A limited number of men from the Seabees had already been gathered at Waimanolo, Oahu, to form a cadre to train additional demolition personnel. The Seabees were the only Pacific naval unit available at that time that had practical coral blasting experience.

The initiative for this training action was reported to have come from the commander-inchief, Pacific Fleet, Admiral Chester Nimitz's office, in a letter sent to Admiral Turner dated 11 November 1943.

In the aftermath of Operation GALVANIC, in late November, Admiral Turner pushed forward two directives to prevent a repeat of the offshore problems at Tarawa. Turner's first, and most time-constrained, directive required the immediate formation of two Underwater Demolition Teams. The two teams were to be ready for action by the middle of January 1944. The second directive was for the establishment of a secure base in the Hawaiian Islands for the further training of UDTs. This base would later become the Naval Underwater Demolition Training and Experimental Base, Maui.

By the end of November, approximately 30 officers and 150 enlisted men were in training at Waimanolo, Oahu, for underwater demolition work. These men were divided into UDTs 1 and 2. The bulk of the personnel came from NCDUs sent to Hawaii for operations in the Pacific. The balance of the personnel came from the Seabees, Marines (20), and Army (4).

In a letter to Admiral Turner on 9 December, Admiral Nimitz directed that replicas of known Japanese beach obstacles be included in the training going on at Waimanolo. During a 17 December meeting with a joint-force Reef Obstacle and Mine Committee, founded only a few weeks earlier, Admiral Turner discussed the type of unit that would be required to clear coral as well as man-made obstacles from invasion beaches. It was during that meeting that the term Underwater Demolition Team was mentioned for the first time to identify the new unit as separate from the existing NCDUs and Seabees.

The new UDTs were formed up and preparing for their first actions by mid December 1943. The new teams consisted of fourteen officers and seventy enlisted men each and were numbered UDTs 1 and 2. UDT 2 was put under the command of Lieutenant Commander J. T. Koehler. On 23 December, UDT 2 was ordered to San Diego. Once in the States, UDT 2 was attached to Task Force 53, under the command of Rear Admiral Richard Conolly, for Operation FLINTLOCK, the invasion of Roi and Namur in the Marshall Islands. UDT 1 remained in training at Waimanolo, where they were to be assigned to Task Force 52. Admiral Turner was in direct command of Task Force 52, which would attack Kwajalein as part of Operation FLINTLOCK.

In a message to the CNO on 26 December, Admiral Turner requested the creation of the UDTs as active units. This was several days after Turner directed that UDT 2 be sent on to San Diego to prepare for Operation FLINTLOCK. The breach in military protocol was ignored and permission was issued.

On 29 January 1944, Operation FLINTLOCK began with the invasion of several smaller islands in the Kwajalein Atoll, the largest coral atoll in the world. By 1 February, the invasion of the two islands of Roi and Namur commenced. Under the cover of darkness, UDT 2 moved in to the islands in rubber boats. Testing the depth of the waters over the reef, UDT 2 operators didn't find any mines or other obstacles. The UDT 2 report to the Marines was that the way in was clear. After a very heavy shore bombardment by naval gunfire, the Marines experienced few difficulties or resistance against their late morning landings.

A further target of Operation FLINTLOCK, the invasion of Kwajalein also started on 1 February. During their offshore reconnaissance of Kwajalein, several members of UDT 1 took to the water, going over the side of their landing craft and swimming in over the reefs to check its depth directly. UDT 1 reported the depth of the water as shallow over large coral heads. Tracked landing vehicles were used to land Marine forces because of the UDT's findings. Postinvasion blasting by the UDTs opened paths in to the beaches at Kwajalein through the coral reefs, allowing faster landing of additional men and material.

In March, after Operation FLINTLOCK had been completed, UDTs 1 and 2 were decommissioned. The men and officers were broken up to supply a training cadre with combat experience for the new Maui training base. They also created an experienced core group for newly commissioned UDTs 3, 4, 5, 6, and 7 to be assembled around. The new UDTs would soon see action during Operation FORAGER, the upcoming invasion of the Marianas Islands. At this time it was decided that the UDTs would be completely manned with naval personnel except for liaison officers and observers.

On 14 and 15 March 1944, two basic letters covering the organization of the UDT training base in Maui and the UDTs themselves were issued by Vice Admiral Turner as the commander of the Fifth Amphibious Force, Pacific Fleet. The UDT concept was now established and proven. UDTs would continue to be commissioned to the end of the war.

Normandy And Southern France

The main target of the NCDUs was always planned to be the invasion of Europe and the breaching of Hitler's Atlantic wall. As NCDU units graduated from training at Fort Pierce, they were assigned in increasing numbers to the European theater of operations. Orders regarding the specific mission of the NCDUs were issued in England and the units gathered for training against more specific targets.

One of the targets facing the men of the NCDUs was known as the Belgian Gate or Element C. This massive steel construction was known to be part of the obstacles scattered along the French invasion beaches. Element C was ten feet high, ten feet wide, and fourteen feet long. Built of six-inch-wide steel angle iron that was one-half-inch thick, a single Element C looked like a huge piece of picket fence and weighed close to three tons. And the obstacles could be linked together in long chains, creating a wall of steel posts.

Long experiments with different demolition techniques finally resulted in a way to blast Element C into a pile of steel rubble without turning it into` a lot of lethal flying fragmentation. Lieutenant Carl Hagensen was part of the crew that developed a special charge, sixteen of which could be quickly applied to a single Element C and collapse in one blast. The new explosive charge was made up of Composition C-2, a plastic explosive, packaged in a small canvas bag. During development of the charge, old wool socks were used to hold the explosive before the canvas bags were sewn up.

Now called the Hagensen Pack, the new explosive charges held two pounds each of C-2 explosive and could be very quickly attached to many kinds of targets. The primacord used to detonate the Hagensen Pack could be quickly tied to another long main line of primacord and an unlimited number of charges set off simultaneously. Prior to their operations during the Normandy invasions, men of the NCDUs would spend days assembling thousands of Hagensen Packs for use against the known beach obstacles.

On June 6, 1944, the largest amphibious operation in history began. The target of the huge Allied armada was the beaches of Normandy, France. The U.S. targets were the beaches code-named Utah and Omaha. The initial plan called for waves of infantry and then tank armored support to land first. Under the cover of these units, the men of the NCDUs, reinforced with Army Engineer troops and Navy volunteers, would blast gaps through the beach obstacles. The plan didn't quite go the way it was intended. On Utah beach, the NCDUs and their Army counterparts were able to blast the majority of their assigned obstacles out of the way quickly. On Omaha Beach, the situation was different.

At Omaha, the German resistance was very heavy and losses among the U.S. troops built up quickly. In spite of the inferno of steel and explosions all around them, the men of the NCDUs worked feverishly to blast open gaps through the beach obstacles. The armored support in the form of tanks never made it to the beach, most either sinking on launch or quickly being destroyed by German fire.

In the first day of the landings, a thousand U.S. soldiers were killed, the large majority on a piece of beach now known as "Bloody Omaha." On that blood-soaked ground, 31 NCDU men were killed and 60 wounded. Over 50 percent of the NCDUs assigned to Omaha were casualties. On Utah Beach, six men were killed and 11 wounded.

In the months after D day at Normandy, the NCDUs from Utah Beach were transferred to the Mediterranean theater to join in Operation DRAGOON, the invasion of southern France. On 15 August 1944, the men of the Utah Beach NCDUs joined with the NCDUs who had already been sent to the Mediterranean. The thirty NCDUs joined with the Allied forces in the landings on the French Riviera. These operations went smoothly, for which the veteran NCDU men were thankful.

No losses were taken by the NCDU personnel as they completed clearing the landing beaches of obstacles. Soon after some postinvasion demolition, the men of the NCDUs were sent back to the United States. There, a number of the men returned to their original units or remained with the NCDUs and moved on to the Pacific and the UDTs.

Water Is Never Cold: The Origins of the U.S. Navy's Combat Demolition Units, UDTs, and Seals Naval Combat Demolition Units (NCDUs) and Underwater Demolition Teams (UDTs), both little-known predecessors of the Navy SEALs, played a crucial role in the Pacific and European theaters during World War II. As the vanguard for amphibious assaults, they were tasked with beach reconnaissance, depth sounding, and clearing obstacles, mines, and unexploded ordnance so the troops could land---often while exposed to enemy fire. Their work was as hazardous as it was essential.

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