Wwii Underwater Demolition Teams

[Navy6064]

WWII UNDERWATER DEMOLITION TEAMS


(1943-1945)

Underwater Demolition Teams were the answer found during World War II to the problem which led to heavy Marine Corps losses in the invasion of Tarawa in the Pacific in 1943, and which faced the Allied Expeditionary Force before the invasion of Normandy in 1944.




The waves of landing craft carrying troops of the famous Marine Second Division onto the beaches of Tarawa, went aground on a submerged coral reef which had not been revealed by aerial reconnaissance photos about a mile and a half from the beach, thus forcing the troops to wade the long stretch in hip deep water under withering Japanese fire. Losses were thus tragically high before the landing force was even afoot on the Island. It was painfully apparent to staff planners of all services that the success of future amphibious invasion of Japanese held territory would be in jeopardy if there was to be no way of knowing what obstacles, both natural and man-made, lay to seaward of the beach, and if there were no way of clearing such obstacles.




In the meantime the plans were nearing completion for the invasion of the German held Normandy coast by the Allied Expeditionary Force. It was evident that the Germans' initial line of resistance would be mines and underwater obstacles designed to stop the invasion craft. Navy planners therefore conceived the Combat Demolition Units, which would go in with the first wave at Normandy and supplement the Army beach sappers who were faced with the problems of clearing gaps through barbed wire, walls and tank traps.

The first personnel were garnered from the CB's, the Navy Construction Battalion Men, and from the early Navy/Marine Scout and Raider Volunteers who were rugged and capable physically and who had previous swimming experience. They were collected together at Fort Pierce, Florida, in the early summer of 1943. An intensive physical training program was devised, apparently based on the theory that a man is capable of about 10 times as much physical output as is the normal conception. Demolition work was emphasized and non-restricted. Methods were developed for demolishing the type obstacles expected at Normandy. Grueling nighttime problems conducted in the snake and alligator infested swamps of Florida produced a specimen of man who was at home with mud, noise, exhaustion, water, and hostile beings, human or otherwise.

The graduates of the school were organized into small 6 man units, which were called Navy Combat Demolition Units, and a large number were sent to England to join the large invading force in the winter of 1944. No one there knew exactly what they were or what to do with them and it was only after many weeks of being shipped around to various stations and being used merely for watches and guard duty, that they were finally able to settle down for training and invasion rehearsals. Additional men were picked up to swell the units from all sorts of commands, and though previously untrained, these men were fitted into the six man and one officer units.

These men were our original ancestors and no amount of honor bestowed upon them will be excessive; they will always have a place in the rank of history's gallants. The story of the two American beaches at Normandy, Utah and Omaha, has been recorded in detail and is available in many sources. Operations on Utah beach proceeded with relative ease and pretty much as planned, but at the same time Omaha Beach was like the entrance to Hell. The NCD Units accompanied the assault infantry in the boats of the first wave.

The NCDU men did not anticipate any swimming, for the clearance was to be conducted at low tide. They wore impregnated, hooded, canvas fire fighting suits, with field shoes and long stockings, also impregnated. A protective mask covered the bare part of the face; this garb was in anticipation of a spray of mustard gas.The invasion force was wet and seasick after the two day delay on the rough channel. As they neared the beach it was obvious that the preliminary bombardment had been made and lifted on schedule, but the cloudy skies had made it impossible for planes accurately to hit the enemy strong points.

The Germans had reserves available at Omaha and immediately replaced losses at bombarded bunkers. As the boats neared the beach the enemy fire began to fall. Within minutes the water was littered with debris and wrecked craft, and many demolition units were wiped out altogether. An example of the discouraging losses in this H-Hour period was the fact that out of some 20-30 amphibious tanks which were to give supporting fire, only four were seen in action. The Demolition Men proceeded nevertheless to set up charges at their assigned gap spots. There was no shelter on the side sand field, and the men worked as though in a rainstorm, only instead of rain there was shrapnel. The disorganized and misplaced infantry were seeking shelter behind some of the charged obstacles, and were tripping over the detonating cord lines laid out between obstacles. In four places however, they heeded the purple warning flares, and four gateways to France were unveiled with tremendous triumphant explosions. The NCDU losses at Utah were 30%, and at Omaha about 60-70%, giving an over-all average loss of 41% men lost in the assault.

The survivors of this great day were shipped to the Pacific to form the nucleus of the great force being formed. They had not utilized their swim training in Europe but were now to do so. The lessons of Normandy were applied to the amphibious problems of the Pacific Islands, and the basic tactics were developed that still are the basis for operational procedure today. The concept of 6-man NCDU was changed to embrace a structure of Underwater Demolition Teams, consisting of 100 men and 13 officers, two or three of which comprised a unit,and in turn, several of these units comprised squadrons.

Basic training was still conducted at Fort Pierce, Florida, followed by six weeks of advanced training at Maui, Hawaii, which became a staging area for advance operations. The main story of UDT comes out of the Pacific operations which were all done in approximately the same manner. The highly developed methods made UDT operations an effective and well invested weapon and after the Normandy operation until the end of the war, losses were only about 1%. 28 or 29 Teams were now in combat operations; Borneo, Peleliu, Saipan, Tinian, Guam, Lingayen and Leyte Gulfs, Iwo Jima, and in conclusion, Okinawa. At the end of the war there were 34 teams in commission, about 3500 men in all.

They were all combined into 5 tremendous teams designated A, B, C, D, and E for purposes of demobilization. The thousands of fins, coral shoes and face masks were stored in warehouses and the reservists went back home to their civilian occupations and lives; the others were sent to duties on ships and stations as their individual rates called for.

The above history was written in 1960 by W.H. Hamilton, Jr., Commander Underwater Demolition Unit TWO



During WWII there were 32 individual UDT Teams with over 3,000 men total.

[Navy6064]

The Underwater Demolition Teams were a newly formed unit. They were designed to chart beaches and pave the way for amphibious landings. Training for the swimmers was vigorous. The men were made to swim miles in jellyfish infested waters. Often men would have to be pulled out of the water, from being stung so many times, because they could no longer swim. All of this training was an attempt to form men who would go anywhere and would feel no pain. Men who would compete the mission, no matter what the cost.



Tasks

Underwater Demolition Teams were responsible for performing the following tasks: "hydrographic reconnaissance, beach clearance, and the demolition of underwater obstacles" (Stubblefield and Halberstadt, p. 99). All of these missions were very important because they were all necessary in order to prepare for an amphibious landing. They helped to pave the way for the landing of Marines on Normandy shore (D-Day).

HYDROGRAPHIC RECONNAISSANCE

The first of these tasks is hydrographic reconnaissance. The purpose of the hydrographic reconnaissance mission is to find out what the beach is like. These missions can be carried out by anywhere from 2 swimmers to 50 swimmers depending on the size of the beach and the amount of information needed. When searching for underwater obstacles, anywhere from 25 to 50 swimmers were used. The swimmers are dropped off far out to sea and swim in to between 25 and 50 yards off shore. Then they assemble a line parallel to the shore. Once in line, the swimmers begin searching for underwater obstacles. They do this by diving down and swimming in a zigzag pattern. By swimming in a zigzag pattern, the swimmers are able to maximize the amount of area they cover searching for obstacles. (See diagram below)



Other purposes of the hydrographic reconnaissance mission were to take samples of the sand on the beach. These on-the-beach missions were usually carried out by one or two swimmers. The fewer swimmers out of the water the better, because it is very easy to detect the swimmers on the beach, however, it is difficult to detect the swimmers in the water because only their heads are showing. The beach is analyzed to see what type of support it will give to heavy equipment. It is difficult for tanks and heavy troop carriers to move if the sand is too soft. While taking these samples, the swimmers also look to see what type of defenses are located on the beach, if there are sentries and if there are any visible obstacles or mines on the beach. Once the swimmers are done with the on-the-beach reconnaissance, they quietly slip back into the water and swim out to sea where they are joined by the rest of the team and are picked up by a waiting ship.

BEACH CLEARING

Once this task is done, the next mission is to clear the beach obstacles that are in the way, so the amphibious landing can take place. The next night, the swimmers return to the beach with explosives. They place their charges (ranging from TNT to explosive hose) around the obstacles and then tie all the charges into a single detonator (commonly called a "hell box"). The swimmers then swim out to sea and detonate the charges.

UNDERWATER OBSTACLE CLEARING

Underwater obstacle clearing is done at the same time that beach obstacles are cleared. Underwater obstacles are cleared by placing waterproof charges around the obstacles. All of the charges are then tied into a single detonation cord, which ties further into a detonator. The swimmers then swim out to sea and the charges are detonated, clearing the obstacles. Usually, the beach charges and the underwater charges are placed and detonated at the same time, that way the swimmers only have to go close to the shore once under the reasoning that the closer to shore you are, the more dangerous it is, because it is easier for the enemy to see you.

DIVERSIONS

Sometimes it was necessary to make the enemy think that a certain beach was going to be attacked, when in fact, it wasn't. This tactic is called a diversion. UDT's would perform this tactic by swimming up to a beach that was not going to be used for an amphibious assault. They would then begin a "recon" (reconnaissance) of the beach and the area around it, making it obvious that they were there. This way the enemy would know that something was going on. Next, they would place demolitions on the beach and on obstacles (if there were any) in the water. They would then swim out to sea and set off the charges. By doing this, the enemy would think that something is going on out there, and therefore, the beach they are guarding is going to be used for an amphibious landing. The enemy will call for reinforcements, which will divert defenses from other beaches that are going to be used for the actual assault. This type of diversion mission was done at the same time that hydrographic reconnaissance missions were being conducted at the beach to be used for the landing. Therefore, two teams were needed; one for the diversions, and one for the actual reconnaissance. The diversion mission is extremely important because if it is not successful, then the other hydrographic reconnaissance mission will have been in vain.



Equipment

Underwater Demolition Teams used different types of equipment to accomplish their missions. The first combat swimmers had little swim equipment. Often they would plunge into the ocean with little more than a pair of canvas swim trunks. Masks, breathing systems and cold water suits were not yet being used by the Navy (Stubblefield and Halberstadt, p. 99). These early combat swimmers usually had no more than a knife attached to their belt for protection. However, when the UDT's knew that they would be going into a dangerous situation, they could ask for gunfire from Naval Destroyers. These Destroyers were extremely accurate and were able to suppress most of the enemy fire the UDT's were facing on the beach. The shelling was extremely successful for getting rid of snipers located on the beach.