The city of Liege was devoid of defenses with the exception of two outdated forts, The Citadel, and La Chartreuse, which were built in the early 1800's. The enceinte that surrounded the city had long since disappeared. The trend in the 19th Century was to move the city defenses to the outskirts. This was necessitated by the advent of long-range artillery of higher caliber and velocity. Thus the ring fortresses came into existence in the major cities of Europe.
One of the most extensive ring fortresses surrounded the city of Antwerp. This strategic Belgian city was protected by older masonry fortifications but they were too close to the city center and could not resist bombardment by the latest artillery weapons. The foremost military engineers of the times began to experiment with concrete and steel protection. Forts would present a lower profile and be built to blend into the terrain. Gun embrasures, first constructed with metal plating, evolved into armoured turrets. Europe's armament firms, like Krupp's and St. Chamond, competed for business in the rage of fortress construction that swept Europe in the latter half of the 19th Century.
One of Europe's most well known military engineers was Henri Alexis Brialmont (1821-1903). He was the son of General Laurent Brialmont (1789-1885), who served under Napolean and later became aide-de-camp to King Leopold I and Belgium's Minister of War. His father's military ties helped Henri to gain entrance to the Ecole de Guerre. He graduated in 1843. He became well known as a prominent fortress entineer and was sent to Antwerp to modernize that city's ring of forts.
Brialmont published 35 volumes and 74 brochures on fortress engineering and related subjects. He pointed out the siege of Ostend from 1601-1604, Wellington's successful stand at the Torres Vedras line in 1810, and the siege of Sebastopol as proof of the power of fortified lines. After working on the Antwerp forts, Brialmont was hired by the Rumanian government to build a ring of fortresses around Bucharest. This project took 12 years to complete and gave him many ideas to use on what would be his final project, the construction of forts around Liege and Namur.
The Brialmont forts were made up of basic components or modules. These components were: the gorge front; the central massif or redoubt; the gallery connecting the central redoubt with the fourth component, the counterscarp coffer. Each component was designated alphabetically and numerically, and combined to form a fort that adhered to the surrounding terrain.
Four types of forts were constructed around Liege:
A total of 12 forts were constructed. The average distance between the forts was 1900 meters. The largest gap was 7000 meters. The perimeter of the fortress ring was 52 kilometers and the average distance from the city center was 6.5 kilometers.
Six forts were located on each bank of the River Meuse. On the right bank, situated from north to south, were:
On the left bank, from north to south, were:
General Description of the Forts:
As mentioned previously, each fort was either triangular or quadrangular. From ground level, the fort presented a low profile. Approaching the fort, one would see clear terrain sloping upwards. This was the outer glacis of the fort. Rising above the top of the glacis to a height of 1 meter was a concrete mass. On top of the mass were turtle-shaped steel cupolas. From a distance, very little of the fort showed. From above, as seen from a bird's eye, the picture was quite different.
Each fort had a central redoubt surrounded by a dry ditch. A counterscarp wall enclosed the 8-meter wide ditch. Triangular forts had 3 salient angles (I, II, and III), quadrangular forts had 4. Each ditch was designated by the two salient angles it connected (ditch I-II, II-III, etc.). At the rear of the fort (the base of the triangle or quadrangle), on the reverse slope of the position, facing away from the angle of attack, was the entrance to the fort. This entry postern led to the counterscarp caserne, which consisted of flanking guard chambers protecting the entry postern, storerooms, kitchens, bakery, laundry, communications, and latrines. The entry postern, which ran the width of the counterscarp, opened up into the dry ditch.
On the opposite side of the ditch was the gorge front caserne, also facing away from the enemy. This gorge front was bastioned in the larger forts and contained 2 casemates which flanked the ditch with enfilade fire from 5.7cm rapid-firing guns. A 5.7 in a third casemate was trained across the ditch on the entry postern. This gorge front contained a second entry postern leading into the interior of the fort. On either side of the postern were additional quarters for the troops, as well as munition storage. The rear faces of the forts were weakly protected with 1.5 meters of concrete. Each chamber had a window which opened out onto the ditch. These windows could be covered over with steel bars for additional protection against shelling.
Behind the gorge front and protected by 2.5 meters of concrete, was the central massif. This was the heart of the fort and contained the main guns, water cisterns, powder and shell magazines, plotting rooms, and machines for heating and electrical power generation. A staircase led up from the entry postern of the gorge front into the central massif. At the base of the massif were two sets of stairs which served as an exit for the infantry to the surface of the fort (terreplein). On the surface, infantry parapets and locations for mobile 5.7cm guns (which were stored in covered shelters on the surface) and machine guns surrounded the perimeter of the central redoubt on the crest of the earthen glacis which sloped down into the ditch on angles I-II and II-III (III-IV in quadrangular forts).
The central massif was made entirely of concrete. The armored weapons turrets were embedded in the concrete. The large caliber guns (120mm, 150mm, 210mm) were for long distance targets. 5.7mm guns in turret provided defense for the approaches and could sweep the outer glacis of the fort to a height of 1 meter at an angle of -6 degrees.
At the head of the triangle, or in the top two corners of the quadrangle, was a casemate equipped with guns to provide flanking fire down the angle of the ditches. This casemate, or coffer, was built into the 5 meter high counterscarp wall. It was two stories high and was connected to the central massif by a tunnel.
Concrete thickness of the curtain wall, flanking casemates in the gorge ditch, and the gorge front caserne was 1.5 meters.
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