The outer line of Germany's coastal defense zone is in the sea itself, where patrol boats (Vorpostenboote) cruise in the English Channel and the North Sea, and along the rest of the Atlantic Coast of Europe, not only to flash warnings of hostile aircraft but to give the alarm if a seaborne force approaches. Minefields bar the way through strategic waters, and closer inshore, along the landing beaches, the Germans have embedded steel and wooden obstacles just below the water's surface to trap assault boats and tank-landing craft.

Then, from the water's edge and for miles inland, the terrain that is favorable for invasion along the coast of Europe is organized in depth with coastal defenses, field and permanent fortifications, and airfields.

The defenses are especially elaborate along the coast of France, Belgium, and The Netherlands. Since the beginning of the Allied campaign in North Africa, however, the Germans have hastily begun to improve the fortifications of the northern Mediterranean coast. Italy, too, with German collaboration if not under outright German control, has started to mend her defenses in the south and on the islands of Sicily and Sardinia.

This study is based mainly, however, on the defenses that have been developed on the western coast of France and the Low Countries, these being the most modern, and the most typical for purposes of illustrating German methods. Any variations in other regions are due mainly to different local conditions and types of terrain; for example, camouflage and the disposition of emplacements amid the sand dunes of Belgium would naturally differ from those on the rocky sides of a Norwegian fiord.

But despite all their efforts, the Germans have not been able to entrench themselves on every mile of the coast line of the occupied countries. Some positions have had to be weakened in order to conserve forces for the Eastern Front. In some places, no doubt, the defenses are surprisingly thin, consisting of nothing more than desolate beaches, protected by one or two lines of barbed wire, minefields and machine guns, and patrols of small units.

Permanent or improvised, all of the German defenses can be breached or reduced by troops who have been thoroughly trained and adequately equipped. For each type of defense, whether it be a row of steel stakes under water, or a reinforced concrete emplacement, there is a technical method by which that type can be destroyed. Equipment, technique, and tactics have been developed for dealing with the fort and its immobilized fire power.