Field Marshal Erwin Rommel was charged with protecting the Nazi-controlled French coastline from Allied invasion.
Field Marshal Erwin Rommel devised a diabolical array of defenses to protect the French coastline. Allied forces, however, developed their own innovative countermeasures, which ultimately won the day.
Underwater dangers
Rommel figured that the Allies would attack at high tide, shortening the stretch of sand soldiers would have to cross to reach the back of the beach. He had his forces submerge several lines of obstacles in the near-shore waters that would be invisible at high tide, creating a death trap for approaching boats. Farthest out to sea was a line of timber posts, cocked at a seaward angle, with Teller mines attached to the top. Each 20-pound mine carried about 11 pounds of explosives, triggered to explode when a pressure of about 330 pounds was put on the detonator in the center of the mine. The blast could destroy a jeep, or blow the tracks off a tank. Next, Rommel placed a row of “Czech hedgehogs,” devices sculpted from three metal girders or pieces of rail line welded together at the center. The steel structures could rip out the hull of a boat. Rommel also used metal “Belgian gates,” log ramps, and “tetrahedrals” — metal pyramids with triangular bases — to stop the progress of landing craft.
Allied countermeasure: To the Germans’ surprise, the Allies attacked at low tide, exposing most of Rommel’s hidden horrors. Navigating through the killing field was tricky, but not impossible.
Higgins boats, lightweight because they were made of wood, could travel through as little as 18 inches of water and creep over logs and other obstacles.
Torrent of bullets
Beyond the beach, Rommel and his men constructed some 15,000 concrete bunkers containing machine guns and other medium-caliber weapons. The bunkers were strategically placed to send hails of bullets on criss-crossing paths across the beach.
Allied countermeasure: Low-tide invasion was risky because it increased the exposure of soldiers to enemy fire from the emplacements on the beach. To protect the arriving soldiers and bring them as far up the beach as possible, the Allies employed a modified version of the shallow-water Higgins boat, first developed by Andrew Higgins in the 1930s for use in the swamps and marshes of Louisiana. Higgins boats, lightweight because they were made of wood, could travel through as little as 18 inches of water and creep over logs and other obstacles. Each 36-foot-long boat could carry a crew of 36 men, a jeep and 12 men, or 8,000 pounds of cargo up onto the beach, then turn around and head back to sea to get more troops and supplies. The Allies also moved men in duplex-drive, or DD tanks. Each DD tank was a modified Sherman tank. Two steerable screw propellers were added to the rear, which enabled the tank to glide through calm water at about a walking pace. A nine-foot-high canvas skirt held in place with inflatable struts was erected around the tank, increasing its buoyancy and keeping it afloat (and also making the tank look like a more harmless boat). Once on land, the tank’s regular tracks took over to drive it up the sand. DD-tanks, designed under the supervision of British General Percy Hobart and one of his collection of “Funnies,” were used mostly by the British. The Americans had their own amphibious vehicle, the single-propeller, six-wheeled DUKW, or “duck” truck, which was shaped like a boat with a hollow airtight body. The duck (or “Donald Duck”) could carry 25 soldiers and their gear, or 5,000 pounds of cargo.
Uncrossable clay
The beaches of Normandy offered Rommel another unanticipated defense: A soft, blue clay beneath the surface sands that could bog down even the most powerful tank.
Allied countermeasure: Allied spies discovered the soft sand during reconnaissance missions to Normandy before D-Day, which gave Percy Hobart time to design the “Bobbin” tank, a modified tank rigged with a huge spool at the front end. A carpet embedded with steel mesh was reeled onto the spool. As the tank moved forward, the bobbin laid down the carpet, providing a solid footing for the tank and other vehicles that followed.
Buried mines
Up on the beaches, Rommel and his men created a mine field, with millions of tank- and-jeep-destroying Teller mines buried beneath the sand. Rommel had wanted some 300 million mines for the French beaches; by D-Day, he and his troops had laid down just over 4 million — still a formidable obstacle.
Allied countermeasure: The hidden mines were impossible to spot and avoid, so Percy Hobart designed a tank that would safely blow them up. The front of his Sherman “flail” tank, also known as the “Crab,” was outfitted with a 10-foot-long spinning cylinder to which 3-foot-long heavy chains were attached; the ends of the chains held fist-sized steel balls. As the tank crept forward, the chains were whipped around and slammed into the ground at a depth of several inches, detonating the buried mines.
Barbed wire
In the event that invading forces managed to get past the shore and beach defenses, Rommel placed yet another obstacle at the back of the beach: long lines of loosely strung concertina wire. While taut barbed wire seems more dangerous, a loose wire is actually more difficult to cross, easier to get tangled in, and harder to escape.
Allied countermeasure: Sherman flail tanks were able to take out many stretches of wire. Soldiers also used the portable M1A1 Bangalore torpedo, first used by the British in India in 1912, to blow out holes in the concertina wire. A single torpedo could take out a section of wire about six feet wide.
