Defense against amphibious attack at sea remained a Kriegsmarine responsibility and the navy had both deep-water mines and coastal mines for this mission. Deep-water mines are largely outside the scope of this book, but in the event they were not particularly significant on D-Day. Due to the strong currents in the Seine Bay, minefields had to be periodically refreshed to be effective and there were not enough mines available to do so regularly. As a result, Naval Force West's preferred tactic was dubbed "Blitzsperren," or lightning barrage; the idea being that the mine-laying force would wait until an invasion was imminent and then sortie forth and quickly laid minefields. An effort to deploy mines in the Seine Bay off the invasion beaches on the night of May 23, 1944, was frustrated by Allied counteraction after the plans were discovered in advance by an Enigma signals intelligence decrypt, leading to a highly effective Royal Navy and RAF attack on German minelayers. After the Dieppe raid, the Kriegsmarine showed more interest in deploying controlled minefields in shallow water. These were used primarily in port areas such as Cherbourg and Le Havre, and not off the rest of the Normandy coast due to the time and expense of creating and operating such minefields. The Kriegsmarine developed an inexpensive, mass-produced, shallow-water anti-craft mine called the KMA (kustenmine-A: coastal mine-A), which consisted of a concrete base containing a 75kg explosive charge surmounted by a steel tripod frame with the triggering device. Although cheap and effective, they became available too late. They were first laid in the high-priority areas along the Channel coast from Boulogne south-westward towards Le Havre by early June 1944. The next area to be mined was the Seine Estuary around Le Havre, which was to begin on June 10, but this never took place due to the invasion. The lack of KMA mines prompted Rommel's headquarters to develop a family of improvised anti-craft devices that could be built in large numbers using locally available materials. In March 1944, Naval Group West developed and tested their own Nussknackermine (Nutcracker mine), which was an improvised copy of the KMA using a concrete base containing an explosive device such as a French high-explosive artillery projectile, with a pivoting steel rod that pressed against the projectile fuse when a landing craft came in contact with it. Other improvised coastal mines used the same concept but different methods of mounting and triggering the explosive charge. Deployment of these began in April 1944, initially at priority locations including the Channel coast and Brest. The performance of these improvised mines was erratic due to the effect of water on submerged munitions not designed for submersion. In addition, German garrisons in some sectors found that the mines tended to be damaged or upset by tidal currents, with the triggering beam being particularly vulnerable. Simpler anti-craft mines such as the Minenpfahl were created using conventional land mines such as the Teller anti-tank mine, mounted on stakes along the shore. The Schwimmende Balkenmine consisted of several Teller mines strapped to a wooden raft that was held in placed by a rope or chain fastened to a concrete anchor. The Armsperre mine placed a single Teller mine on a float, and then fixed the mine using chain or metal bars to a concrete anchor, creating a cheap coastal equivalent of conventional naval mines. The effectiveness of these mines was mixed due to the effect of seawater on mines not designed for frequent emersion. However, the motto at Rommel's headquarters was "better to do something imperfect than nothing at all" The Schwimmende Balkenmine was an improvised anti-craft mine consisting of a half-dozen Teller mines strapped to a wooden raft. These were anchored off the invasion beaches to concrete bases or to other obstructions. In the background is one of the ubiquitous Czech hedgehog obstructions. There were never enough high-explosive devices to create coastal minefields along the entire Normandy coast, so Rommel and his headquarters developed a variety of obstacles to interfere with landing craft. This was Rommel's single most important contribution to the defence of the Normandy coast. During a visit to Hardelot-Plage on February 3, 1944, Rommel was shown a technique developed locally by troops of using a high-pressure water hose instead of a pile driver to emplace wooden stakes. This took only three minutes per stake as compared to 45 minutes using a pile driver. Subsequently, Rommel ordered this technique to be used in Normandy to create extensive obstacle barriers of Hochpfahlen (high stakes) created from telegraph poles, metal beams and other material. In some sectors, such as Sword Beach, the rocky conditions did not permit the use of fire hoses, and the slower pile drivers had to be used. In the haste to create these barriers, little attention was initially paid to their actual effectiveness in stopping landing craft. In mid-February 1944, the Seventh Army tested some of the obstacles using a British landing craft captured at Dieppe. The landing craft plowed through many of the obstacles, especially the stakes. As a result, more substantial Hemmbalk (beam obstructions) were developed based on a tripod design. The less substantial vertical stakes remained in use, but often improved by the addition of mines as mentioned before. Another addition to the stakes was the stahlmesser metal saw teeth to cut into the lower hull of the landing craft. Hemmbalk were a more substantial obstacle developed in the spring of 1944 when it became evident that the simpler stakes were not effective against an on-rushing landing craft. They were usually topped with a Teller mine to blow a hole in the hull of the landing craft.
Besides locally created obstacles, Rommel also sponsored an effort to collect existing obstacles from fortified areas elsewhere in Europe that were not being used at the time. The Tschechenigel (Czech hedgehog) steel anti-tank obstacles were collected, as their name implies, from pre-war Czech fortified areas. They were transferred to Normandy and fixed in shallow water by embedding their steel arms in concrete anchors. Another common obstacle in the coastal waters of Normandy was the Cointet obstacle, also known as Belgian gates or "C-elements." Cointet obstacles, also called Belgian gates or Element C, were widely used as obstructions on the Normandy beaches. These were large steel obstructions designed by Col. Leon De Cointet in 1933 for the Maginot Line. Although rejected by the French Army, some 75,000 were manufactured for Belgium and they were used along the border to obstruct roads. Many of these 1,400kg obstacles were collected in 1944 and deployed off the Normandy coast, as well as in the intended role as road obstacles further inland. Besides these captured obstacles, tetrahedron obstacles were mass-produced in Germany or locally assembled, and were also used in Normandy to thicken the shallow-water obstacle belts. German troops install a steel tetrahedron along the Normandy shore in the spring of 1944. These were usually secured by concrete anchors. By June of 1944, the Fest.Pi.Stab 11 of 84th Corps had completed 205km of continuous coastline obstructions out of the 320km of coastline under its responsibility. Priority had been given to coastal areas more likely to be assaulted, so beaches edged by cliffs were the last to receive attention. All of the D-Day beaches had obstacles installed, though some were more effectively blocked than others. For example, stretches of the beaches near Utah Beach proved unsuitable for many of these obstructions due to tidal action that undermined or washed them away. Sword Beach had less extensive obstacle belts due to the rocky shoreline that inhibited the use of stake obstacles. Areas of the British/Canadian beaches were lined with high sea walls, so this affected obstacle planning. While the average density of obstacles along the Normandy coast was about 260 per kilometre, the D-Day beaches had much higher densities than average, ranging from a low at Sword Beach of 300 per kilometre to a high at Omaha Beach of about 490 per kilometre. Those at Omaha consisted of 3,700 obstacles including 450 ramps, 2,000 stakes, 1,050 hedgehogs and 200 Belgian gates. The table below summarizes the extent of this obstacle effort. Beyond the coastal obstacles, the Wehrmacht deployed an array of conventional barriers including barbed-wire entanglements and minefields. The minefields were generally located beyond the beaches, as the tidal action tended to disrupt any planted on the beach itself. Through the end of 1943, some 1.7 million mines had been laid in belts along the coast, and Rommel planned to expand this to 50-100 million mines. This did not prove feasible as the rate of supply from Germany at the time was around 40,000 mines per month, but by the time of the invasion some 4 million mines had been laid along the French coast. The 716th Infantry Division, which was responsible at the time for the D-Day beaches, laid 62,000 mines by February 1944, increased to 100,000 by March 1944. Due to the shortage of conventional mines, there were several different types of improvised mines used in Normandy. There were several hundred thousand French naval gun projectiles in arsenals that were converted into mines by fitting contact fuzes. Some of the beaches lined with cliffs had improvised mines deployed, made from old French or German artillery projectiles. The Minengranaten were simply artillery rounds strung on the cliff with an impact fuse that would fall off and explode if disturbed. The Rollminen were a more deliberate weapon, consisting of a similar artillery round and impact fuse, but lashed to the cliff by a rope that had to be cut for the mine to fall and explode. US troops on the western side of Omaha Beach encountered these types of improvised mines.
Since mines were not well suited to the beaches due to tidal action, the Wehrmacht planned to deploy a less conventional alternative, the Goliath remote-control demolition vehicle. These small tracked vehicles were controlled via a wire that trailed from a spool at the rear. They were intended to be steered against high-value targets such as landing craft and tanks, and when they were near their 60kg (130Ib) explosive charge could be remotely detonated. They were generally positioned under cover in small individual shelters near the beach. Only a few units received these in time, such as the platoons along Utah Beach, while other units received them a few days before the invasion and did not have time to properly prepare them for use, such as the platoons stationed on Omaha Beach. A variety of conventional techniques were used to obstruct tank movement off the beach, including anti-tank ditches, anti-tank walls, concrete caltrops/tetrahedrons (Betonigel) and various types of steel anti-tank obstructions such as the Eiserne hemmkurven, a type of prefabricated curved anti-tank ramp. The Wehrmacht attempted to use the Goliath remote-control demolition vehicles for coastal Defence against the Allied landings at Anzio and again in Normandy, in both cases without success. This is a small underground shelter for a Goliath created near WS on Utah Beach which proved to be ineffective when the preliminary bombardment severed the control wires. Rommel also insisted that the areas immediately behind the beaches be prepared against paratroopers and glider landings. Larger fields were studded with vertical posts that were intended to interfere with glider landings. There were plans to link these stake defences together with wire obstructions but this was not completed before D-Day. Efforts were made to mine main suitable landing zones, but a shortage of mines limited the effectiveness of this program. Besides these obstacles, a program began in the spring of 1944 to flood the tidal areas behind the beaches. This was intended both to limit the available fields suitable for glider landing and to serve as a barrier to mechanized advance off the beach by Allied forces. In most respects, the flooding operations proved to be far more successful in complicating Allied airborne landings plans than did the obstacles, which were not robust enough to actually stop a glider landing.
Belgian Gate Wheeling a "Belgian Gate" into position on the foreshore a massive construction of angle-iron designed to disembowel landing-craft. There were other unpleasant surprises, too but never enough of them to satisfy Rommel.
Belgian gates or "C-elements." I wonder what was done with the majority of the Belgian gates or "C-elements."?That was a lot of barriers that was used in Normandy shores and road closures.
