The Atlantic Wall (German: Atlantikwall) was an extensive system of coastal defences and fortifications built by Nazi Germany between 1942 and 1944 along the coast of continental Europe and Scandinavia as a defence against an anticipated Allied invasion of Nazi-occupied Europe from the United Kingdom, during World War II.

The manning and operation of the Atlantic Wall was administratively overseen by the German Army, with some support from Luftwaffe ground forces.

[a] Today, ruins of the wall exist in all of the nations where it was built, although many structures have fallen into the ocean or have been demolished over the years.

[3] Less than a month after this victory, Adolf Hitler issued a directive stating that Germany must be ready for an offensive through France and the Low Countries.

[3] However, the Oberkommando der Wehrmacht (German high command; OKW) was convinced that preparations would take at least until the following year.

[3] Prior to the Atlantic Wall decision, following a number of commando raids, on 2 June 1941 Adolf Hitler asked for maps of the Channel Islands.

[8][9] The Regelbau (standard build) system used books of plans for each of over 600 approved types of bunker and casemate, each having a specific purpose, having been updated as enemy constructions were overrun and examined, even testing some to destruction for effectiveness.

OT was the chief engineering group responsible for the design and construction of the wall's major gun emplacements and fortifications.

[14] Efficiency of the OT decreased in late 1943 and 1944 as a result of manpower pressures, fuel shortages and the bombing of worksites, such as V-weapons sites, where some volunteer workers refused to work in such dangerous areas.

Daily, weekly and monthly reports showing progress, work variations, material used, stocks of material, labour hours used per skill type, the weather, equipment inventory and quality, level of supervision, employee absences, staffing levels, deaths and problems experienced all had to be filed with the OT.

[13]: 57 Throughout most of 1942–43, the Atlantic Wall remained a relaxed front for the Axis troops manning it, with only two large-scale British attacks.

Operation Chariot, launched near St Nazaire in March 1942, successfully destroyed German pumping machinery for, and severely damaged, the Normandy dry dock and installations.

[16] Early in 1944, with an Allied invasion of Nazi-occupied Europe becoming ever more likely, Field Marshal Erwin Rommel was assigned to improve the wall's defences.

[9] In likely landing spots for gliders and parachutists, the Germans emplanted slanted poles with sharpened tops, which the troops called Rommelspargel ("Rommel's Asparagus").

Hitler had decreed that one-twelfth of the steel and concrete used in the Atlantic Wall should go to the Channel Islands, because of the propaganda value of controlling British territory.

[19] The islands were some of the most densely fortified areas in Europe, with a host of Hohlgangsanlage tunnels, casemates, and coastal artillery positions.

As most of the German garrisons surrendered peacefully, the Channel Islands are host to some of the best-preserved Atlantic Wall sites.

Hitler ordered all positions to fight to the end, and some of them remained in German hands until Germany's unconditional surrender.

[36] Although the defensive wall was never fully completed, many bunkers still exist near Ostend, Channel Islands, on Walcheren, near Scheveningen, The Hague, Katwijk, Noordwijk, Den Helder, and in Scandinavia (Denmark and Norway specifically).