Naval Combat Demolition Units
It became apparent that in addition to the Scouts and Raiders, a group of specialists to destroy obstacles was required. In late 1942, a group of Navy salvage personnel received a one-week concentrated course on demolitions, explosive cable cutting and commando raiding techniques. The Navy Scouts and Raiders unit was first employed in Operation Torch, the invasion of North Africa in November 1942.[6] During Torch, this unit cut the cable and net barrier across a river in North Africa, allowing Rangers to land upstream and capture an airfield.
The NCDU teams, each consisting of one officer and five raiders were to clear the beaches of obstacles for the invasion force with the team coming ashore in an LCRS inflatable boat with their explosives.[7]
Naval Demolition Units landed as part of the Allied invasion of Sicily; they were divided in three groups that landed on the beaches near Licata, Gela and Scoglitti.[8]
In 1943, the Navy decided to create a large dedicated force for such tasks: the Naval Combat Demolition Units (NCDU). On May 7, Admiral King, the CNO, picked Lieutenant Draper L. Kauffman USNR to lead the training, which was based at Fort Pierce.
The expansion of the force meant recruitment beyond the pool of experienced combat swimmers. Most of Kauffman's volunteers came from the Seabees (the Navy's Construction Battalions), the U.S. Marines, and U.S. Army combat engineers. Training commenced with one grueling week designed to "separate the men from the boys". Some said that "the men had sense enough to quit, and left the boys." It was and is still considered the first "Hell Week."
Kauffman's experience was at disarming explosives; now he and his teams were learning to use them offensively. One innovation was to use 2.5-pound (1.1 kg) packs of tetryl placed into rubber tubes, thus making 20-pound (9.1 kg) lengths of explosive tubing that could be twisted around obstacles for demolition.[9]
At the beginning of November 1943, six men from Kauffman's Naval Combat Demolition Unit Eleven (NCDU-11) were sent to England to start preparations for the Normandy invasion. Later NCDU-11 was enlarged into 13-man assault teams. Weeks before the invasion, all available Underwater Demolition men were sent from Fort Pierce to England. By June 1944, 34 NCDU teams were deployed in England.
Normandy
The Germans had constructed intricate defenses on the French line. These included steel posts driven into the sand and topped with explosives. Large 3-ton steel barricades called Belgian Gates were placed well into the surf zone. Reinforced mortar and machine gun nests were dotted along the beaches.
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 debris spread along the beaches, thereby creating more of an obstacle. The NCDU found that the best method was to sever the key corner joints in a gate, so that it fell down flat.
According to the Allied attack plans, infantry supported by naval gunfire would make the initial landings, followed by tanks and troop carriers to clear any remaining German bunkers and snipers. The NCDU teams (designated Demolitions Gap-Assault teams) would come in with the second wave and work at low tide to clear the obstacles. Their mission was to open sixteen 50-foot (15 m) wide corridors for the landing at each of the U.S. landing zones (Omaha Beach and Utah Beach).
Unfortunately, the plans could not be executed as laid out. The preparatory air and naval bombardment was ineffective, leaving many German guns in position to fire on the attackers. Also, tidal conditions caused many of the NCDU teams to land prematurely - in some cases ahead of the first wave. Despite heavy German fire and resulting casualties, the NCDU men planted charges and demolished many obstacles. As the infantry came ashore, some soldiers took cover on the seaward sides of obstacles that had demolition charges on them. They quickly moved onto the beach.
The greatest difficulty was at Omaha Beach. By nightfall only thirteen of the planned sixteen gaps were open, and of the 175 NCDU men who went ashore there, 31 were killed and 60 were wounded.
The attack on Utah Beach was much more successful. There, only four were killed and eleven wounded, when an artillery shell hit a team working to clear the beach.[4]
NCDUs also participated in Operation Dragoon, the invasion of southern France.
NCDUs also served in the Pacific theater. NCDUs 2 and 3 were transferred there, and formed the nucleus of a group of six NCDUs.
History
The first UDTs to use that designation were formed in the Pacific Theater.
Tarawa
The invasion of Tarawa in November 1943 nearly met disaster due to obstacles in the surf. Tarawa lies in eastern Micronesia. The islands in this region have unpredictable tides and are surrounded by shallow reefs that block even shallow-draft craft, except at a few narrow channels or at high tide. At Tarawa, the attack went in at low tide, due to inadequate knowledge of local conditions, and the surrounding reefs were exposed. The Amtracs carrying the first wave crossed the reef successfully. But the LCVPs carrying the second wave ran aground on the reef. The Marines had to unload and wade to shore. Many drowned or were killed before making the beach. The first wave, fighting without reinforcements from the second wave, took heavy losses on the beach. It was a painful lesson that the Navy would not permit to be repeated.
Admiral Kelly Turner, the Navy's top amphibious expert, ordered the formation of nine Underwater Demolition Teams. As with the NCDUs in Europe, the personnel for these teams were mostly Seabees. These volunteers were organized into Combat Swimmer Reconnaissance Units, becoming the Navy UDTs.[6]