Some German Views on Fortifications, WWII Tactical and Technical Trends, No. 21, March 25, 1943 (Lone Sentry)

A. ELEMENTS OF MODERN FORTIFICATION DESIGN

The German army was noted in the early stages of this war for its offensive operations, but the German High Command has not neglected the art of defensive warfare, in which fortifications may play a major role. The following article, translated from a German military review (1941), presents a summary which is regarded as representing certain aspects of German theory on the design of modern fortifications.

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a. General

Like all the means of waging war, fortifications have been subject to constant change throughout the course of history. New methods of attack give rise to new designs in fortification, and new designs similarly force the development of new means of attack. Every war brings new experiences. Nevertheless, simple basic designs can be recognized, designs that remain uniform at the core. In what follows, these will be discussed especially from the tactical viewpoint, and without consideration of the operational significance of the fortification.

Every fortress is a reinforcement of the terrain, and results from the effort to increase further the superiority of emplaced weapons against a mobile attacker. The defender can choose his position, his "emplacement" in the terrain, and can reinforce and strengthen it according to the time and materials available. On the other hand, the attacker of fortifications is forced to penetrate the defender's position with strong means of assault, or at least so to interdict the defender's action that the attacker can move in close and overcome him in close combat. Even fortifications that lead the attacker to give up the idea of making an attack have fulfilled their purpose.

b. Fundamental Principles

The objective of the defender is to annihilate the attacker by fire. For this purpose, fortifications must withhold their firepower until the moment in which it can be used to decisive effect. Until that time the fortification must provide cover against the effect of the attacker's arms. The attacker's fire effect will be further weakened or dispersed if his observation is made difficult by the concealment of the defensive positions.

Fire effect, cover, and concealment are, therefore, the basic considerations that determine the forms of fortified positions, and which must always be weighed against each other in their development and application.

These factors are mutually related: they complement each other in part, but they also interfere with each other. It is impossible to achieve the ideal of a perfect combination, but a calculated and planned combination must be made. Sometimes the main aim to be attained in the combination of these factors can be determined by tactical considerations; how this aim can be achieved under given circumstances depends on the individual case. Fire effect has priority over cover: concealment increases and provides a substitute for cover up to a certain point; adequate cover reduces the importance of concealment. However, poor concealment facilitates enemy observation and thereby his operations; faulty concealment can thereby nullify the fire effect planned for the decisive moment. In modern fortifications there is no fundamental distinction between permanent fortifications (i.e., those developed with the means available in peacetime) and field fortifications, except that construction of the latter is limited by war conditions with respect to the outlay of time, labor, and materials possible. In the case of permanent fortifications, the basic designs can be developed and perfected to a correspondingly greater extent.

c. The Shelter

The simplest form of fortress is the shelter. It is an example of a form that developed in field fortifications and has found a place in permanent fortifications. In their modern form, small in size and accommodating only one or two squads or gun crews, shelters can be scattered throughout the battle position and can provide possibilities of cover everywhere. Small as targets, they are easy to conceal, and this can be done most completely by sinking them to the level of the ground surface. Technical limitations may be met if the water table is high. In every case the entrance to the shelter must be higher than the water table, even though account must be taken of the increased costs when the construction must be done in ground water, and when water-proofing must be arranged for.

The disposition of shelters on the terrain depends on the fire plan. In addition, to meet unforeseen battle situations, some shelters may be used to contain reserve units.

In modern fortification practice, shelters are made of reinforced concrete. The thicknesses vary according to the mission of the emplacement, and according to the type and penetration power of the arms expected to be used by the attacker. In the case of small and well-concealed shelters, one can take into account the fact that the effectiveness of attacking arms will be relatively limited. With the methods used in permanent fortifications, shelters can easily be fitted out so as to make them livable for long-term occupation. The degree to which shelters are livable has tactical significance, since it helps in determining how long a group can garrison the shelter without relief. The longer this period, the fewer total effectives are needed.

However, shelters are merely cover: fire effect is not possible from them, and the garrison has to leave them for firing assignments and combat. Here arises a serious danger: that in large-scale battle, if the attacker covers the emplacement with heavy fire and smoke, the defenders will not recognize in time the decisive moment when the enemy infantry nears the position. The attack may reach the advanced shelters and put them out of action before the defenders can emerge and organize their defense.

This danger must be met primarily by arrangements for suitable observation. It is difficult, however, to guarantee that the arrangements will function at the critical moment. The solution may be sought by using telescopes which can be sighted in any direction, in armored observation towers, or by using observers in exposed or partially protected positions. The first method has the disadvantage of spoiling the complete concealment which is the major advantage of a shelter, and the second method lessens the protection afforded to personnel.

Even if they have been installed in advance, firing emplacements which are open and have covered approaches or lateral communications can betray the locations of shelters to enemy observation; therefore these open emplacements demand great care in construction.

d. The Loophole Position

Summing up, it may be said that as regards cover and concealment, shelters can be developed almost to ideal perfection--but at the cost of the fire effect. The more attention given to cover and concealment, the less assurance that the planned fire effect can be realized at the decisive moment. These disadvantages of the shelter are reduced if it is made possible to fire from the shelter (or from some special combat space in it), thus combining cover with fire effect. The simplest means for accomplishing this is the loophole, and the result is the loophole position.

(1) The Wall Loophole

The simplest design is the wall loophole. This can be used for observation when firing is not in progress; in the latter case, a second loophole is needed unless the loophole has been widened to permit both observation and fire. The loophole position, however, has a disadvantage: concealment is largely sacrificed in the interest of fire effect. The loopholes must be placed above ground level; often, in fact, rather high above it because of vegetation. Additional space, above the loopholes, is necessary for the movements of the gunners, and the cover must come above this space. All this means a rather high structure. Only in particularly favorable conditions, for example on rising ground, can the structure be adapted to the ground and thereby given suitable concealment.

In addition it is necessary to allow sufficient space for traversing and elevating the gun in order to obtain adequate fire effect. The result of this requirement is loophole "mouths" of greater or lesser size, depending on the wall thickness. These mouths can hardly be camouflaged without diminishing observation and reducing fire effect. Especially in the critical moment when the gun goes into action, these mouths are easily detected and attacked.

The size of the outer openings can be reduced by designing the loopholes in the shape of an > < in this case the guns are emplaced partly in the thickness of the wall, and this arrangement makes it easier for the crew to swing the gun laterally. However, by this arrangement the gun no longer has the protection of the full thickness of the wall. This disadvantage can be reduced, but not eliminated, by armor-plating the loophole.

(2) Loophole Armorplate

The logical carrying out of this principle leads to the development of loophole armorplate; with only a fraction of the wall thickness, this armorplate can offer the same resistance as the thick reinforced concrete. The loophole opening can be made correspondingly smaller. Nevertheless, the open loophole is still easy to detect, especially since the armorplate is harder to camouflage than a concrete wall. Nor can this disadvantage be eliminated by special construction of the loophole shutter. The place where a vertical piece of armor-plate is joined to the reinforced concrete structure is a weak point, and requires special attention in designing. Furthermore, the elevation of the structure remains unchanged. To reduce the elevation, one possible solution is to use a flat roof of armorplate. Even in this case, a considerable cubic volume is still needed to give room for handling the gun and the crew--aside from the fact that the structural joints become more complicated, and that construction costs are greatly increased by the use of armorplate. These disadvantages are especially notable in the case of frontal loopholes, and so another possible solution is by siting guns for loophole flanking fire only. This solution, however, simply substitutes one problem for another, since frontal fire is absolutely indispensable for repelling attack. Furthermore the terrain often gives the attacker opportunities for flank observation, and positions for combatting these flanking loopholes--or, the attacker may acquire such vantage points in the course of the battle.

(3) The Loophole Position and the Fire Plan

An advantage of the loophole is that, up to a certain point, it permits the preparation of an almost automatic fire-plan. The place of each gun in the fire plan is clearly indicated by the position of its loophole. But here again is a point of weakness: if guns are put out of action, gaps in the fire may develop, especially if the defender is depending on the "automatic" functioning of his fire plan. A fire plan with overlapping fires, arranged in depth, minimizes this weakness but increases the number of installations and weapons employed. Therefore, the exclusive use of loopholes imposes a certain rigidity on the defense, and does not permit the defense to adapt its fire to changing and unforeseen combat situations. Some guns may remain idle because, in their sector, no target is visible to them, while in other places the guns may not be adequate to combat the targets offered. This problem can only be met by a defender who is energetic, and who views the loophole position only as a shelter cover which must be abandoned if necessary in the interest of fire effect.

(4) Large Weapons in Loophole Positions

The difficulties in installing loophole positions increase with the size of the guns. Fire missions will occur in which emplacement behind loopholes seems desirable and suitable not only for machine guns but also for guns of larger caliber, especially antitank guns. These larger guns are the ones which can or should be limited in their field of fire to a specified sector. In the case of cannon, the problem of embrasures is even more difficult, since, apart from the size of the weapon, a greater clearance is needed for aim, especially with regard to elevation. The result is rather complicated and expensive construction.

On the other hand, guns emplaced in cover are thus provided a certain measure of protection and better possibilities for concealment (i.e., in comparison with open works), although these possibilities are limited in the case of aerial attacks. Further improvements may be made by providing bomb-proof quarters, in shelters, for the gun crews and for ammunition, and by arranging routes of withdrawal and alternate positions. A simple problem, and one which can be easily solved, is the installation of high-trajectory weapons under cover from which they are capable of firing. High trajectory fire is especially effective in supplementing and overlapping frontal fire.

e. The Armored Turret

Perhaps the most compact form of combat position is the armored turret, consisting of armorplate with a circular base and a rounded cover. This form affords enemy fire the smallest target and the least favorable surface of impact. Its elevation is kept down to the indispensable minimum needed for the service of the weapon. Also, the solid union of an armored turret with the concrete block offers no great structural difficulties. On the other hand, turrets are very costly. Protection can be obtained in any degree desired by varying the thickness and quality of the material, but the question of cost and the technical problem of transportation weight here approach their maximum limits. Even in the case of turrets, we find the opposing, interacting relationship between the objectives of fire effect and concealment. The latter is very difficult if great fire effect is to be achieved.

Turrets may stand in the open and thus have an all-round field of fire, or they may be built into the terrain and have a field of fire limited to a predetermined sector. A turret with only one loophole affords the smallest possible target and can thus be adapted to almost any terrain. However, a turret loophole gives no more tactical fire effect than any other loophole, and it costs much more. If the number of loopholes is increased to two or three, giving a firing radius of 200 degrees, this immediately complicates the factor of concealment because the semi-circular form of turret necessarily becomes more visible. However, the turret with several loopholes does solve one major problem in the arrangement of the fire plan. Even more important, it permits the same weapons to be used for other missions when they are not serving their principal mission in the fire plan. In this way the rigidity of the prepared fire plan is to a certain degree reduced, and thus a weakness is remedied. Furthermore, several loopholes make it possible, at least in emergencies, to use several guns. The multiple-loophole turret thus gives a much greater fire effect, without additional expense.

The advantages just discussed are gained especially in the case of turrets constructed for all-round fire: either with guns mounted so as to rotate inside the turret, and fire through a number of loopholes, or with the turret itself so constructed as to rotate. The rotating turret is more expensive and demands special provision for the protection and operation of the rotating mechanism. Such turrets realize a maximum fire effect with a minimum use of space, but they can at best be only incompletely concealed.

This disadvantage is eliminated by building disappearing turrets, which are raised out of their cover only for firing, but this naturally involves a further complication and expense. In addition there is the difficulty of observation and the problem of determining the correct moment for raising the turret. At that moment no concealment is possible, although the fire effect may be increased by the element of surprise involved. Even heavy weapons, especially cannon, can be built into turrets. For these weapons, only rotating turrets can be considered; otherwise the dimensions become too great and fire effect is severely limited. The protruding barrel of the gun is its most sensitive part; it can, however, be protected by special casing, or can be so designed as to permit easy replacement. Further effective protection can be achieved by the careful siting of the turret on the terrain, care being taken not to spoil the fire effect.

It is particularly difficult to protect antiaircraft guns, but it is relatively easy to solve the problem of sheltering in turrets the smaller of the high-trajectory weapons. Observation posts can also be set up in turrets.

f. The Combination of Defensive Elements

Shelters, loophole positions, and turrets are the basic units which enter into the design of all modern fortifications. The central problem of all fortification design turns on the construction of the positions from which the fire effect must be achieved, and on their adaptation to the terrain. In the construction and lay-out of all shelters which are designed not for combat but for the convenience and comfort of troops, the purely technical possibilities and the questions of cost are the determining factors.

It is a significant fact that a greater number of weapons or living quarters can be more cheaply assembled in one larger structure than in many single units. From the standpoint of tactical considerations, the latter type of lay-out offers the advantage presenting a smaller target, adapting itself better to the terrain, and permitting a more thorough control of an area. In the larger structure, it is possible to achieve the combination of various arms and greater numbers of combat effectives under more closely unified leadership, as a center of resistance.

Thus we have many forms in modern fortifications: so many as to be confusing when all are viewed at once:

(1) Simple (and more complex) shelters for accommodating gun crews, as well as for special purposes such as serving as a command post or providing storage space for rations, ammunition, and reserves.

(2) Loophole positions (single or multiple loopholes), with or without adjoining shelters.

(3) Combat positions with turrets, to contain various weapons or to be used as observation positions, likewise with the necessary adjoining shelters.

(4) Smaller and larger aggregates (or works-Werke) with various weapons, behind loopholes or in turrets, with adjoining rooms and mechanical installations.

(5) Larger combinations of works and single positions, with gallery connections to separate works and groups of works.

g. Entrances and Communications

A further problem is presented in the matter of entrances. On the number and size of the entrances depends the speed with which the crew can emerge from cover in case of need.

On the other hand, every entrance offers a possibility of attack to the enemy and must therefore be given special protection. High entrances under strong cover have deep recesses, and it is therefore particularly difficult to camouflage them. They complicate, and also impede, exit. Armor-plated entrances reduce this disadvantage, but in their turn increase the cost.

When open communications are used, trampled paths will result in spite of all precautionary measures, and the aerial photograph of these paths betray even installations well camouflaged against surface observation. Open communications, also, are not safe under enemy fire. The difficulties connected with both entrances and communications can be relieved by using gallery communications. These permit covered liaison, the supply and transfer of effectives, and simple bombproof routes for telephone lines as well as for supply lines of all sorts. Bombproof resting rooms, command stations, mechanical installations, and depots for rations and munitions and the like, can be connected with these galleries with relatively little additional cost. On the other hand, they require a considerable outlay in construction time and cost, if their bombproof quality is not to be nullified. Favorable earth and ground water conditions are prerequisites for the technical possibility of constructing such works.

h. Obstacles

Finally, obstacles must also be considered among the types of permanent fortifications. Obstacles are erected against infantry and tanks, principally in front of the main line of resistance, but they may also be effective deep within the main battle position. They result in a considerable heightening of the fire effect, because they impede the attacker in his forward movement and thus to a greater degree force his exposure to the effect of the defensive weapons. The obstacles must therefore lie within the effective range of the defensive weapons and must be dominated by their fire. Here, especially advantageous use can be made of flanking and diagonal fire. The obstacles will in general be erected continuously, but gaps may serve to canalize the enemy attack in accordance with the intentions of the defenders. Observation and fire coverage of the obstacles must be maintained also at night and in fog. An important requirement is that the obstacles must not interfere with one's own observation and field of fire, even when allowance can be made for supplementing this fire by high-trajectory weapons. It is very important, in addition, that the lay-out of the obstacles on the terrain does not enable or facilitate recognition of the defense system, especially from the air, thereby exposing the location of otherwise well-concealed structures.

Against infantry, wire obstacles are the common form, and are effective when sufficiently wide or when laid in several bands; but dry and waterfilled trenches, reinforced concrete bump obstacles, post obstacles, rail obstacles, and "hedgehogs" of various kinds, especially steel structures, as well as combinations of these forms, are used against tanks. The danger of interfering with one's own field of fire, and the danger that the obstacles may be used as cover by the attacking infantry are especially great in the case of antitank obstacles of all kinds. The former danger can be met by reducing the height of the obstacles; the latter by selecting the least massive form possible and by establishing a fire effect which will enfilade the obstacle. These requirements are often difficult to fulfill in practice. All effective antitank obstacles are high in cost. Mines are arranged and concealed more easily and more rapidly, and leave the field of fire open, but they also constitute a risk to one's own mobility in the forward area. A position on terrain which is impassible to tanks should therefore always be sought, and this factor may under certain circumstances decisively influence the choice of the general position.

i. Conclusion

It was not the purpose of the foregoing discussion to indicate the best form of fortification, but simply to report the problems which arise in preparing them. An absolute optimum form does not exist. Fortifications are a combat medium; in combination they must meet operational requirements, and individually they must meet tactical requirements. As in all such matters, advantages and disadvantages have to be weighed against each other in the particular case; this consideration will determine the location of the fortifications on the terrain, and sometimes their form. Important, further, is the recognition of the fact that no one form guarantees success, but only the fighting spirit and morale of the troops placed in them. To achieve and increase this, good weapons are needed, and also suitable fortification designs. Without the will to fight, however, even the best designs are useless, as the fate of the Maginot Line showed.

B. THE FAILURE OF FORTIFICATIONS IN THE 1940 CAMPAIGN

The following article, translated from a German military review (1941), is interesting in its critical analysis of the weaknesses of French, Belgian, and Dutch fortifications against the German attack in 1940. It is also noteworthy that the writer evidently feels it necessary to argue the point that the experiences of that campaign do not prove that fortifications are outmoded.

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a. General

The press is often accustomed to represent the controversy about permanent fortifications in such a light that the reader has to conclude that their value does not bear a reasonable relationship to their cost in time and money.

The mere fact that every one of the fortified positions attacked by German troops fell quickly, does not in itself justify any conclusion as to the value of permanent fortifications. In the war on the Western Front, weaknesses on the opposing side favored our successes.

Without any desire to minimize in the least the unprecedented achievements and offensive power of our troops, the following must still be said:

A permanent fortification that is to be fully equal to its mission must meet the following requirements:

(1) It must block all avenues of attack (even those that seem hardly practicable), leave no gaps suitable for breakthrough, and be uniformly strong everywhere. (It must be understood, of course, that a weaker type of lay-out can be compensated for by favorable terrain.)

(2) In estimating the strength of construction necessary, attention must be paid to the effects of all modern offensive weapons.

(3) The defense of permanent fortifications must be conducted offensively, as any defense should.

b. French Fortifications

The French land fortifications and their defense met these requirements in some places--in fact, along the entire territorial boundary between Switzerland and the Channel coast, they left no gap--but their strength was quite variable. The strongly developed sectors of the Maginot Line proper (except for the support position at Montmedy (Work 505) which could be approached from the flank) were not seriously attacked. Therefore, a conclusive judgment with respect to these sectors can not be given. The German attacks, except for that on Work 505, were directed only against those portions of the position which were more weakly developed. Because of the type of structure (only individual works in a single line) and the limited strength of the construction, and because of an appreciable lack in depth, portions of the French territorial defense possessed no worthwhile fortifications.

The flaws lay, however, not only in fortresses, but also in the spirit of the defense. Not only the inferiority of their air and armored forces, but above all the training and the spirit of the French army weakened the offensive power of the French soldiers and their capacity of resistance. The basic failure, complete concentration on the defensive and a corresponding training program for French soldiers, robbed the fortifications of a large part of their power to repel and to hold. In addition, all of the attacks delivered in June against fortifications were made easier by the fact that artillery and field troops, and even portions of the fortress troops, had been withdrawn from the fortified fronts for the battles in Flanders and for garrisoning the Weygand line.

The French overrated the strength of defensive warfare and at the same time underrated the striking power of the German Wehrmacht, which was combined with special attack tactics for use against permanent fortifications.

A few examples may clarify the points stated:

(1) The first breakthrough at Sedan and to the north struck the junction between the Ninth and the Second Armies (Corap and Huntziger). At this place, where a strategic breakthrough was not expected, the prepared position was not only extremely weak and lacking in depth, but both armies, in spite of repeated requests by their leaders, had been given especially poor consideration as to troop reserves and defensive weapons (for example, antitank and antiaircraft guns).

(2) Work 505 (at the Montmedy bridgehead) courageously resisted for almost 3 days, until the entire garrison was dead.

The troops fighting outside the work did, indeed, stubbornly defend the village of Villy, but the garrison was lacking in sufficient offensive spirit to throw back the Germans who reached the area of the fortification.

(3) The attack on a work heavily damaged by shell fire southeast of Weissenburg was shattered by the stubborn defense; further breakthrough attempts here were abandoned.

(4) The breakthrough west of Lembach in the mountainous, forested terrain of the northern Vosges on June 19 was successful because the French garrison had already been greatly weakened (in artillery and reserves) and permitted the attacker to approach unimpeded to within 100 meters from the fortifications.

(5) The many attacks conducted from the rear against the French border fortifications after the breakthrough and encirclement (for example, Maubeuge and west of Rohrbach) met no active defense whatever. These attacks were made easier by the fact that the rear sides of the fortified installations were weaker, and therefore could not resist even light artillery at short range.

c. Belgian Fortifications

The Belgian fortifications were also founded on obsolete notions. The numerous installations of the border defense position were in part not garrisoned adequately, and in part not at all, so that they could hardly be defended against the lightning assault of the Germans. Not one of the major defense positions could be held until French and British help arrived. In their quick collapse, the decisive factor was the surprisingly swift seizure of Fort Eben-Emael. This could be traced back to the fact that the unprecedented courage of the German parachute troop attack had crippled the fort, which in any event had inadequate fire coverage of the area to be defended. Counterattacks were limited to weak attempts from the fort, from neighboring units, and from the responsible 7th Belgian Division.

With the fall of Eben-Emael and the occupation of undamaged canal bridges both at Vroenhoven and Veldwezelt, the whole major defense position collapsed.

The Dyle position would have been able to hold out longer if it, and its extension along the Meuse from Namur, had been developed as far as France. Even the otherwise useful northern sector of Wavre--Lyon--Lierre lacked the necessary depth.

It was therefore a matter of piecework, and south and north of Namur as well as at Wavre, easy breakthroughs were made on May 15. The consequence was that even the northern sector had to be evacuated on May 16.

Even the fortress of Antwerp played no part; its northeastern front was broken through on May 17 without offering noteworthy resistance. The evacuation of the Dyle position on May 16 and the occupation of the city of Antwerp on May 18 made the remainder of the Antwerp bridgehead also worthless.

The bridgehead at Ghent, in itself well developed, both to the north (after the fall of Antwerp and the loss of the lower Scheldt) as well as to the south (after the failure of the British) lost its support and had to be evacuated on May 23.

If one wishes to summarize the value of the Belgian fortifications and the reason for their failure, the following will be admitted from what has been said:

(1) The land fortifications of the Belgians were not eased on a fundamental, clear plan and, in part for political reasons, were much too extensive for the little country and the weak army.

(2) The help of the French and the British, on which the Belgians had counted in planning the strength of their installations, failed.

(3) The attack power of the German Wehrmacht had been underestimated.

d. Dutch Fortifications

What has been said about the Belgian land fortifications applies to an even greater degree in the case of the Dutch fortified installations.

The Dutch attempts to place fortified positions in the way of the German assault shows a deplorable error in judgment, both of the German power and of their own situation. The Meuse-Ijssel position played no role whatever, any more than did the Peel-Raam position, which was broken through at Mill on May 10-11. The Grebbe line held up the attack at Grebbeberg on May 12 only for a matter of hours. In the new positions there was hardly any possibility of an orderly combat leadership, since at no time did they have communications; every loophole position was on its own. The situation of the fortress of Holland was already critical when the German parachute troops on May 10 took possession of the Moerdijk, Dordrecht, and Rotterdam bridges--undamaged.

Even under the assumption that the fortifications would only have to hold until the arrival of outside aid, about 4 to 5 days, the main defense position was too weak.

e. Conclusion

If there is any inclination to draw from the role which the land fortifications played in the campaigns of 1939 and 1940 the conclusion that their value did not correspond to the costs of installation, the following should be said in summary as an opposing argument:

(1) The German Westwall accomplished its operative mission of giving the command a free hand in the east. Whether it would have also held against a tactical attack was of course not demonstrated, but it may be assumed with certainty that it would have met-the test, since on the German side the necessary prerequisites had been met.

(2) The fact that the enemy territorial fortifications did not fulfill their purpose was due to the defensive flaws detailed above, or to the incapability of the commanders to utilize them correctly.

Wherever, in individual cases, the defense of the fortifications was inspired with the proper spirit, the results confirmed the permanently sound principle that fortifications increase the combat power of the army, and that therefore, properly used, they cannot be dispensed with.