AvStop Magazine Online
Section I. PASSIVE DEFENSE MEASURES
The great latitude which the airborne attacker enjoys in selecting his target makes it extremely difficult for the defender to take passive defense measures against airborne operations. It is quite impossible to set up antiair-landing obstacles throughout the country. Therefore, no more can be done than to determine what might constitute particularly desirable targets for an airborne attack and in what specific areas air landings directed against these targets might be undertaken by the enemy.
These principles were followed by Germany in taking defensive measures against an invasion in the West, since experience Sicily clearly indicated that the enemy would also resort to airborne operations during an invasion. Accordingly, German antiairborne measures were determined by the following two aims; first, to render useless any points which appeared particularly well suited for landing operations; and secondly, to protect all likely targets against attack by airborne troops.
The first purpose was served by erecting posts approximately 10 feet long and 6 to 8 inches in diameter, imbedded 3 feet deep, connected by wires, and partly equipped with demolition charges. These obstacles were intended to prevent the landing of troop-carrying gliders. German experience showed that such post obstacles are effective only if they are equipped with demolition charges. If no demolition charges are used, although the glider may crash, the enemy will still be able to make a successful landing.
Mining and flooding the terrain were additional measures. The former can be effective against gliders as well as airborne troops if the enemy lands at the very point where the mine field has been laid. However, since such mine fields are necessarily limited because of shortage of materiel and personnel, it is really a matter of luck if the enemy happens to land in a mine field. Furthermore, in the interest of one's own troops, the local inhabitants, and agriculture and forestry, it is impossible to consider extensive application of this method. Undoubtedly, flooding large areas by means of artificial damming deters the enemy from landing at the particular spots. This method, in addition to others, was widely used on the Atlantic coast. Unfortunately, however, at the time of the invasion, some of these flooded areas had dried up again because of lack of rain.
Laying mine fields and flooding areas serve a twofold purpose if, by their location, they not only prevent airborne landings but at the same time constitute obstacles against attack on the ground.
In order to protect potential targets, preparations were made for allaround defense by establishing fortifications, obstacles, and barriers and by wiring bridges for demolition. These are measures which have to be taken everywhere in modern warfare-not only against airborne operations but also against penetrations by mobile forces on the ground, against commando raids, and in occupied territories against partisans and rebels. Wherever they were adequately prepared and reinforced by the necessary personnel, they served their purpose.
Orders for resistance against invasion on the Atlantic coast called for an inflexible defense in which the coast constituted the main line of resistance. To counter any simultaneous large-scale airborne operations, instructions were issued to develop a "land front" several miles inland, with its rear to the coast. In this manner, it was intended to establish a fortified area between "ocean front" and "land front" which was to be defended like a fortress, thus preventing the juncture of the enemy elements attacking from the sea and those landing from the air. During the invasion, however, the Allies did not oblige by landing their troops inland beyond the land front, but landed them either into it or between the two fronts. Furthermore, since the German land front was occupied by insufficient forces because of a shortage of personnel and since it had not been adequately developed, its value was illusory. As a matter of fact, the obstacles, such as flooding, at some points even protected Allied airborne troops against attacks by German reserves.
Experience taught the Germans that passive measures have a limited value against airborne operations. Furthermore, in view of the great amount of time and materiel required, they can be employed only where the fronts are inactive for a long period of time. In mobile warfare, the only passive measures to be applied are preparations for an all-around defense carried out by all troops, staff, supply services, etc., behind the lines.