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Towards the modern fortification


Written by Sakhal

The fortification after the Middle Ages: the castle and the wall change to withstand the artillery

The first cannons benefited the defense of castles more than their siege, mainly due to their low power and short range which characterized these incipient firearms. Medieval castles resisted the impacts and forced the attackers to a certain proximity, exposing them to the projectile weapons and cannons used by the defenders, who being at a higher position benefited from an improved range. Because of this the castles of the 15th century preserved their traditional defensive structure, with the only variation being the addition of loopholes and occasional gunports in their walls, placed in a very sparse way to avoid weakening the structure.

But the perfectioning of the techniques used for manufacturing cannons and powder brought more powerful and safer firearms to the battlefield, cannons which could fire from beyond the range of the weapons used by the defenders metallic projectiles which could not be stopped by the walls of medieval fortresses. The concept of the medieval castle had to change to keep the fortresses impregnable. The tall walls of medieval castles were now an inconvenient because they were large and easy to collapse targets. The new walls were built with a lower height and sloped instead of vertical faces, which greatly increased their resistance. They were made thicker not only to endure the impacts from the enemy artillery but also the growing weight of their own artillery. It was very important to further extend the bastion or clear area which surrounded the castle to fight the attackers from a greater distance. In the bastion defensive obstacles were placed which could be well covered by the defensive weapons of the castle.

As aforementioned, the height of the walls constituted a disadvantage regarding their resistance, but in the other hand it was necessary for avoiding the potential assaults. The only solution was to build the castle in the middle of a wide and deep moat, rising from the ground level just the necessary for harassing the attackers. It was soon seen that the higher height of the towers was an inconvenient for moving the heavy artillery pieces and ammunitions to more compromised zones, for which reason they began to be built with the same height than the walls, and soon the polygonal fortress without towers made apparition, which would be so effective as the medieval castle was in the past.

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One of the forts built by Henry VIII along the southern coast (left picture), from Kent to Cornwall, is a clear example of the transition period from the medieval castle to the modern fortress. It was an experiment for building a fortress-castle in the search for a definitive solution, which did not arrive until the implantation of the Italian polygonal system, which was already in an early stage of development when this fortress-castle was built. The perfectioning of the artillery provided ships of the line and frigates with enough firepower for forcing to think of the defense of the coastal cities from possible bombardments from the sea. Hence, maritime forts were built in strategic points of the coast (right picture), which were polygonal forts adapted to the configuration of the terrain.

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The battlements of medieval castles no longer granted protection against the new artillery, so they were replaced by solid and spaced gunports with an artillery piece placed on each of them to grant protection to the artillerymen (left picture). Also the loopholes changed. Before they were used for bows and crossbows and now they would be used for firearms, so a hole for the barrel was added (right picture). But this happened only during the transition period, for in the polygonal fortresses the loopholes were allowed only in the (corner) turrets.

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In the 17th century castles had been already replaced by fortifications or strongholds. The defenses of a fortification were constituted by a wide bastion, composed of diverse obstacles, all of them of polygonal construction to facilitate cross-fire and a deep defense. It was extremely dangerous to approach the fortifications without protection, but the attackers had their own approach methods, such as field gunports, sand bags and approach by means of parallel trenches based on sap and gabion. It should be noted that these trenches were not used in open field battles, where everything was solved through closed formations of infantrymen until the advent of automatic weapons in the beginning of the 20th century.

The following picture depicts the Bastion of Vauban from the late 17th century. The slope in front of the first defensive level is called "glacis" or "scarp". The first defense level is the "counterscarp" where a front line of riflemen would take cover. The second defense level has a moat and a small circular fort or "pillbox". The third defense level had a thick bastion of sloped faces on whose top artillery pieces were placed. After the bastion there was a wider moat and thereafter the stronghold, fitted with gunports for artillery pieces and turrets for riflemen.

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The following patterns are typical layouts used in polygonal fortifications; the first one is from the 17th century and the second one, which is simpler and more effective because of having fewer blind spots, is from the 18th century.

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For the defense of the strongholds powerful wall rifles were developed. Because of their dimensions, conception and usage, wall rifles, used during centuries in the defense of walled cities and fortresses, are between the long infantry rifles and the small field artillery pieces. Sieges to cities and military strongholds were part of any military campaign during the 17th and 18th centuries, and wall rifles played a prime role for their defense. They were heavy and long firearms of large caliber and long range, with a capability of penetration which was very superior to that of infantry rifles, from which they did not differ much regarding their structure. Simply their size was carefully increased and a metal support was added to their fore part to allow them to rest in the wall. This also helped to hold the violent recoil caused by the notable powder charge. Due to not being personal weapons these rifles lacked slings or bayonet attachments. They were aimed mainly at the most dangerous elements in the battlefield, namely officers or artillerymen.

The rifle just below was built around 1680 in Regensburg; it has a caliber of 26 millimeters, a length of 1.94 meters and a weight of 25 kilograms. The buttstock has an artistically sculpted animal head and the rest of the rifle is ornamented by some vegetal motifs. The firing trigger includes a spring to rearm it and the trigger guard is shaped to adapt to the fingers. The safety lever and the head of the hammer are missing on this particular rifle. The other rifle further below, which has the same purpose, was built around 1750 in Potsdam; it has a caliber of 23 millimeters and a length of 1.61 meters.

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The fortification in the 20th century: the concept of trench redoubt is adopted to withstand the new artillery

Long before 1870 the system of polygonal bastion already suffered from a certain unbalance regarding the evolution of artillery. Albeit, as it had happened two centuries ago, in principle such evolution benefited more the strongholds than the attackers, because the powerful and heavy steel rifled cannons, were hard to transport, maneuver and emplace, being much more efficacious in the fixed emplacements of the fortifications. However, the extraordinary ranges achieved by the field artillery pieces forced to think of a new fortification system, for the bastion system demonstrated to be excessively vulnerable. It was necessary to locate the outer defenses increasingly farther from the defended site, to keep at a safe distance the enemy cannons.

Since the construction of a concentrical continuous enclosure at two kilometers from the stronghold would be very expensive it was adopted a network of forts, separated but arranged in such a way as to cover with their fire the whole line to be defended. The idea of separated forts promptly thrived and before the end of the 19th century they were already profusely used, either for protecting strongholds or frontier perimeters, in similarity to medieval castles. But the constant progress of cannons and explosives put in evidence the defects of the new tactic. In 1904 the Russian forts at Port Arthur did not withstand the fire from the 11-inch (280-millimeter) howitzers of the Japanese. The problem did not stem from the concept of separated forts, but from the inadequate protection of each of these defensive elements.

Because of this it was reinforced the theory of the trench redoubt developed by the German author Johannes Schroeter, who, following the idea of separated forts, advocated the utilization of low defenses, enclosed by a barbed-wire perimeter, protected by a moat of six meters in depth, used as well for protecting the artillery pieces, machine gun nests and barracks, besides reinforced concrete and steel. The diffusion of this type of fortification caused as a logical reaction the apparition of field artillery pieces of huge caliber, which could be moved and emplaced only after facing extraordinary difficulties. Such scarce mobility could have been the cause, at a strategical level, of the origin of the failure of the German offensive of 1914.

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The following picture depicts a belt of forts of the trench redoubt type which protect a stronghold (upper left), the top-down view of one of the redoubts (upper right) and the cross section of this very fortification (below). The redoubts depicted in this example are scattered throughout an extension of several kilometers to form an archetypical defensive complex of the early 20th century.

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[1] Esplanade with barbed wire [2] Riflemen's line of fire [3] Five-meter deep moat with barbed wire fence [4] Defensive facilities of the moat and scarps [5] Observation casemate [6] Armored artillery turret [7] Reinforced concrete shelters under the front wall [8] Moats [9] Two-story barracks [10] Blockhouse of the gorge with defensive facilities of the moat

The new characteristic which kept the fortifications as valid military elements was the implantation of the upper protection, ceilings strong enough for withstanding the fire from howitzers and mortars. This is why the casemates made of reinforced concrete made apparition (left picture). Sometimes the fortifications were fitted with naval artillery turrets (right picture). In the early 20th century naval artillery was already very well developed, due to the necessity of piercing thick armor plates from long distances. Since naval artillery turrets, albeit designed for being installed on a floating hull, were actually siege artillery pieces they were perfectly adapted to the necessities of the fortresses. Because of this, in some circumstances, it was more practical to install in the forts artillery turrets taken from scrapped battleships.

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On the contrary, in the most important fortifications special artillery turrets fitted with armored cupolas were installed. The cupola and the cannon were retractable and they stayed under the line of fire before and after each shot. When the French retook their fortresses in Verdun in 1916 they saw that the German projectiles had caused minimal damage to this type of armor; but the easy fall of these very forts two years before, as well as those in Liege, Namur, Douaumont, Vaux and other locations, put on the spotlight the actual effectiveness of the allegedly impregnable fortifications.

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The machine gun

During the Great War of 1914-1918, where the most acerbated infantry combats in History took place, the machine gun stood out in a lugubrious way, as a weapon equivalent to a hundred of men, so dangerous that already in the Russo-Japanese War of 1904-1905 the Russians called it the devil's water can. Machine gun "nests" became essential elements in the fortifications for their high volume of fire could keep infantry assaults at bay. The machine gun was a prime demoralizing element for the infantry, in conjunction with another two brutal warfare means developed during the Great War: the flamethrower and the lethal gas.

Since the age of arrow machines capable of shooting multiple projectiles had been tested. After the discovery of powder there was no lack of ingenious inventors who tried to solve the problem of multiple and continuous shots. Because of this a great diversity of coarse repeating automatic weapons made apparition, based on the principle of attaching multiple small-caliber barrels into a single piece. After igniting the first barrel all the charges were ignited in a correlative way. But such contraptions, known as organ batteries, were more spectacular than effective. They had three fundamental defects: the difficult reload, which was effectuated through the muzzle, the lack of a way to stop the shooting after the ignition and the impossibility to aim while shooting, which forced to send the whole volley to the same direction. These shortcomings caused the discredit of these weapons, taking into account as well that a normal cannon loaded with shrapnel caused the same effects.

It was required to achieve a machine which could be aimed while shooting shrapnel in a correlative way and which could be reloaded as quickly as possible. Regardless of how many experiments were carried out by skilled inventors of different periods none of them achieved the objective, simply because the solution lied in the metallic cartridge. Once this one was achieved, machine guns made apparition everywhere, and some of them were really interesting. These first machine guns were of manual operation, which means that the whole mechanism was actuated by hand through either a crank or a lever. They were still not very effective, due to the effort required to operate them, but enough for being present in all the conflicts from the American Civil War to the end of the 19th century. The most effective and popular of machine guns actuated by hand was invented by Richard J. Gatling in 1861. It was operated through a crank and had a theoretical rate of fire of 500 to 600 rounds per minute, but some later models were perfected to the point of reaching up to 1200 rounds per minute.

But the first truly modern machine gun was that created by Hiram Maxim in 1884, in which the whole movement of its mechanisms was actuated by the recoil force from the shots. During the First World War all the armies were equipped with diverse models of Maxim machine guns. The German used the Model 1908 depicted in the following picture. It was a weapon of caliber 7.92 millimeters fed by belts of 250 cartridges which could be joined together; it had a theoretical rate of fire of 600 rounds per minute and a muzzle speed of 800 meters per second. Some Maxim models were still in use during the Second World War. The barrel and stock recoil mechanism of the Maxim was used as well by other brands such as Fiat, Wickers and Schwarzlose; even that regarded as the best machine gun of the Second World War, the German MG-42, operated through this system.

In 1895, John Moses Browning patented a machine gun which obtained the force for its automatic movement through the utilization of just a small part of the explosion gases. Also this procedure of taking the gases from the barrel reached a huge development in Europe during the First World War, and several very effective models made apparition, among which the brands Hotchkiss, Lewis, Saint-Etienne and Colt (this latter used by the American during the Cuban War of 1898) stood out. This system became the most widely used in automatic weapons, because despite being not as smooth as that used by Maxim it has undoubtful advantages which render it more interesting.

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In the Hotchkiss machine gun depicted in the picture it can be clearly seen the place where the gases from the cannon are taken through a very small orifice, which is enough for pushing with strength a piston which is connected to the mechanisms of the weapon. The range and the rate of fire are similar to those achieved by the other system, since the small escape of gas does not practically affect the prestations of the weapon. The pressure created in the breech during a shot reaches around three tonnes and half per square centimeter, which is a huge proportion in comparison with the few kilograms which are diverted for automatizing the weapon.


The outwitted fortification

The Second World War started, especially regarding the material aspect, where the First World War ended; elements such as aircraft, tanks, artillery, rifles, uniforms or transmissions were similar despite including the logical technical progress. But at a strategical level, those who were more convinced of this continuity were the French, who took for granted that the next conflict would be one of fixed positions and attrition. Because of this they completely trusted in the fortified line which they had built along the border with Germany, the famous Maginot Line. The German built as well, in front of the Maginot Line, their own fortified line, the Siegfried Line, which was however of lesser importance. Eventually, the Siegfried Line played a role in the defense of Germany in the early 1945.

The Maginot Line began to be built in 1927, when Andre Maginot occupied the Ministry of War. The gigantic construction consisted of a series of fortifications, being almost all of them underground. In the surface, the defenses consisted of casemates made of reinforced concrete and steel, trenches, anti-tank obstacles, barbed wire entanglements and mine fields. In the interior everything was perfectly organized for giving service to the fortified line, as it can be seen in the following picture. The Maginot Line was theoretically impregnable but such affirmation was never proved, since the German surrounded it through Belgium during the Blitzkrieg, albeit there is no doubt that they would have faced great difficulties if they had attempted to attack it frontally.

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[1] Observation [2] Concrete casemates with steel cupolas [3] Aspirator [4] Aeration service [5] Barracks [6] Storage and ammunition for barracks [7] Transmissions and administration bureau [8] Elevator to the cupola [9] Inner railway for artillery service [10] Electricity generator group [11] Powder magazine [12] Troop lodgings [13] Hospital service [14] Storage of victuals and medicines [15] Hoist [16] Service passageway

Fortifications in the Second World War

At the beginning of the war, two opposite strategic concepts, which originated from the experience obtained during the First World War, where huge losses not justifiable by the strategic results achieved were registered, confronted each other. The French generals were convinced that, when facing the modern automatic weapons, a scrupulously defensive position should be assumed to avoid very severe casualties.

The Maginot Line

The French concept of defensive war had its maximum manifestation in the construction of the Maginot Line, a fortification system running along 400 kilometers in the border from the Rhine River to Belgium, formed by three types of constructions. In the foremost zone there was a fixed network of observation posts and first detention, anti-tank barriers, barbed wire entanglements, machine guns and anti-tank pieces, being the whole ensemble accessible from the subsoil. Thereafter there were fortifications which ensured a continuous obstacle to avoid penetrations. The forts were built without altering the landscape and the diverse elements barely protruded from the ground: steel cupolas of 50 centimeters in thickness, armed with cannons of medium and large caliber, turrets with periscopes and wells from where machine guns and cannons of small caliber emerged, being the whole ensemble surrounded by deep lines of barbed wire entanglements, ditches and anti-tank obstacles. In the subsoil, within concrete walls of three to four meters in thickness, they were installed the lodgings, the infirmaries, the storage rooms, the electric power plants, the telephonic centrals, the elevators and the facilities for ventilation and heating. The third defensive system was constituted by fortifications of an even greater size and complexity, armed with cannons of large caliber, besides those cannons and machine guns intended for close defense. The whole system was connected through underground railways.

Alan Brooke, British general who would become Chief of the Imperial General Staff, visited at the beginning of the war the constructions in Welshtenberg and he wrote in his diary: "The fortification reminds of the image of a warship built in the land. It is a masterpiece, and there is no doubt that the concept of the Maginot Line is a brilliant idea. But it grants only a delusive feeling of security, and I think that the French would have done better in spending their money in mobile defenses rather than burying it in the ground."

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The Siegfried Line

Like the British counterparts, the German generals did not try to repeat the "attrition war" which had been the favorite method of the strategists during the First World War. Actually, they preferred a war of movements based in groups of tanks cooperating with infantry units and motorized artillery. Anyway, before the outbreak of the hostilities with France they gave up the offensive precisely because of the existence of the Maginot Line, and finding too risky the advance through Belgium they decided - for having freedom of action in the east - to build a defensive line along the front of the Rhine River, which would be the Siegfried Line. This one was built along 600 kilometers on the Rhine River, the Sarre River and the border with Luxembourg and Belgium. It was designed with a concept different from that of the Maginot Line; not for a static defense, but for a maneuver defense. Because of it the elements were staggered to a depth of 40 kilometers, to serve the purpose of supporting and integrating the action of the mobile forces, to ensure a rather temporary defense.

The foremost zone was fitted with secondary defenses: barbed wire entanglements and anti-tank obstacles laid in continuous lines, and also mine fields, being the ensemble protected by minor constructions, casemates armed with machine guns and cannons of small caliber. Thereafter it was laid a deep fixed network of stronger constructions made of reinforced concrete, but of diverse consistency and arranged following a sort of chequered pattern, and armored cupolas armed with cannons of medium and large caliber. Further beyond there were depots and supply centers. The German entrusted the protection of these constructions to dispersion and camouflage, rather than to armor and concrete walls. The ensemble of the Sigfried Line comprised 22,000 elements of small and large size.

The Eben Emael fort

The 11th May 1940, the German had a sound success in the conquest of the Eben Emael fort, which watched upon the junction of the Meuse River with the Albert Canal. Both the Allies and the German considered this fortress, located in an excellent strategic position, to be the most impregnable in Europe, stronger than any of the forts that the French had built in the Maginot Line. With a series of reinforced concrete and steel passageways built rather deep on the ground, with the artillery turrets protected by thick armor and with a garrison of 1200 men, it was believed that it could resist during indefinite time the largest artillery projectiles and aviation bombs. However, the fortress fell within 30 hours through the action of 80 German paratroopers who landed on its top onboard nine gliders, and whose casualties in combat amounted for six dead and nineteen wounded.

During the previous winter, the German had built in Hildeschein a fort which was identical to the Eben Emael, to train a detachment of paratroopers on how to conquest it. Three groups had to take control of the bridges and the fourth one had to conquest the fort. The group of 80 men who landed on top the fort placed explosive shaped charges on the armored artillery turrets, which put these out of action and also filled with flames and burning gases the lower chambers, causing death to the defenders who were in there. Also flamethrowers were used against the peepholes of the cannons and the observation openings. In just one hour the German managed to enter the upper passageways, to put the heavy and the light artillery out of action and to obstruct the observation posts. The Belgian infantry corps which tried to evict the small group of attackers was repelled by Stuka dive bombers and paratroop reinforcements.

On the morning of the 11th May vanguard armored units crossed the two intact bridges, and after heading to the north they arrived to the fort and surrounded it. After another bombing from Stukas and close combats in the underground passageways, on the noon the white flag was hoisted and the remaining defenders surrendered and left the fort. In Berlin the OKW gave a very mysterious character to this operation when on the afternoon it was announced that the Eben Emael fort had been conquered thanks to "a new attack method". This announcement triggered rumors about a totally new German secret weapon, which could be a gas designed to temporarily paralize the enemies by acting on their nervous system. The truth was indeed more earthbound but not less ingenious.

Two educated opinions about the Maginot Line

Charles de Gaulle

The tactic of the Maginot Line has suffered rough reprobations in sight of the later events. It caused without a doubt a purely defensive mentality, but it is always an excellent caution system to fortify as much as possible a border of hundreds of miles, economizing so the number of soldiers dedicated to a passive service and "channelling" any eventual enemy invasion. If in the general scheme of the war they would have been attributed to the Maginot Line its true importance and an adequate utilization, it could have been extremely effective. It could have been considered as an ample deployment of exit doors of incomparable strategic value and, above all, as a means of preventing the access to larger sectors of the front and accumulating so the general maneuver reserves or "masses". When considering the numeric superiority of the German population in respect of the French one, the Maginot Line must be judged as a wise and cautious measure. Because of that it is strange that it had not been extended at least up to the course of the Meuse; in which case it would have constituted a very efficacious stronghold which would have allowed a free and energic offensive from France. But Marshal Petain opposed the prolongation of the Maginot Line. He stated that in the Ardennes the very nature of the terrain rendered almost impossible an attempt of invasion, and his opinion was accepted. The offensive criteria inherent to the Maginot Line were explained to me by General Giraud during the visit that I made to Metz in 1937. But they were not put into practice, and the Line, besides absorbing a huge number of trained soldiers and technicians, exercised a weakening influx upon the reaction spirit of the French people and upon their military strategy.

Winston Churchill

The idea of a fixed and continuous front dominated the strategy intended for an eventual conflict, and it oriented in such sense the organization, the doctrine, the instruction and the armament. It was intended that in the event of war France would mobilize all of its reserves, constituting the largest possible number of divisions, intended not only to maneuver, attack and take advantage from the success, but to defend sectors. They would have been deployed along the French and Belgian border - Belgium was officially our ally - to await the enemy offensive. Regarding the means - tanks, aircraft, mobile and folding cannons, which already in the last battles of the Great War had demonstrated to be able to achieve the surprise and the breakthrough, and since then they had become more powerful -, the intention was to use them only for reinforcing the frontline and, if necessary, to restore it with local attacks. Thus, the types of weapons had been chosen for such purpose: slow tanks, armed with short and light pieces, intended for accompanying the infantry and not for quick and autonomous actions; fighter aircraft conceived for a defensive role; few bombers and no attack aircraft; artillery pieces made for firing from fixed positions, with a limited horizontal firing arc, which could not move in every terrain nor firing in every direction. Besides, the front was previously traced by the fortifications of the Maginot Line, prolonged in those of Belgium. In this way it was thought that the warring nation would garrison a barrier, awaiting under its shelter that the blockade and the pressure from the Free World wore the enemy down, pushing it to the catastrophe. Such concept of the war matched that of the regime which, lost in a morass because of the weakness of the power and the political discords, should naturally adopt such a static system. But it seems as well that such comforting panacea corresponded too well to the country's frame of mind. Anyone who wanted to be read, elected or applauded had no choice but to take it for good. The public opinion, giving up to the delusion that it was enough to declare war on war itself to prevent the bellicose from making it by keeping alive the memories of many disastrous attacks, and without fully realizing about the revolution caused meanwhile by the engine, did not care about the offensive. In brief, everything contributed to make of passivity the first principle of national defense.


Categories: Engineering - Industrial Revolution - World War One - World War Two - 20th Century

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Website: Military History

Article submitted: 2014-10-24

Article updated: 2020-11-13


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