Polygonal system
In fortress construction , the polygonal system is the principle of avoiding all receding angles as far as possible on the outer lines of fortifications. Fortresses built in this way have the shape of a polygon (a polygon).
history
The term "polygonal system" was generally introduced in connection with the fortification manners of the Marquis de Montalembert and Lazare Carnot (1753-1823). However, the expansion of the fortress by King Friedrich II. In Prussia, which was primarily determined by the fortress builder Gerhard Cornelius (von) Walrawe (1692–1773) and which is described in research as the "old Prussian fortification manner ", can already be seen as the forerunner of the "polygonal system" can be considered (including fortresses Brieg, Neisse, Schweidnitz and Silberberg). In part, this is based on the divided fastening system, such as Hermann Landsberg the Elder. J. (1670–1746) published, but also on specific fortifications in Luxembourg, Mainz or Suomenlinna . After the establishment of the German Confederation in 1815, the (further developed) "polygonal system" initially became the preferred fortification system in the federal states (hence the name "New German fortification manner"), while France officially propagated the bastionary system until 1870 , but in its fortifications since Napoleonic times also used elements of the polygonal system, which the coastal fortifications in France in particular still show today (including Tour modèle ), as well as the fortress project of Lyon (from 1830).
In order to implement the polygonal system, it was necessary to erect capons to flank the wall on the outside . The advantage of the system is that the remote defense of long lines of ramparts is now mainly based on obtuse angles and, by abandoning numerous small external works, can better concentrate on the essential points. Due to the elimination of the bastions and the various outworks of the bastionary system as well as the extensive lines of the tenenill system (a series of angles that jump in and out), a fastening system of significantly less depth results. As a result, more space was gained for the expansion of the cities (which, however, was often not used for the civil settlement, which the example of Koblenz shows well, where the place remained within the limits of the 18th century) and the construction costs were reduced. The separate trench defense was carried out on the inside of the fortress trench by means of free-standing escarp walls and / or galleries as well as free-standing or connected trench capons.
The prototype for the application of the polygonal system in the 19th century was the Koblenz-Ehrenbreitstein Fortress , which was completely rebuilt from 1815 to 1834. In this connection the New Prussian or New German fortification manner is mentioned. An ancient concept that grew out of the confrontational national state thinking of that time. The more recent research avoids this by using the term polygonal system.
New Prussian fortification manner
A first publication by Johann Ludwig von Xylander in 1819 summarized the new fortification principles developed during the construction of the Koblenz Fortress :
- According to the principles of strategy, the fortress is laid out where it intervenes directly in the great operations of wars.
- There is no generally binding system of fortresses, as no system is ideal on every terrain. Instead, there are fastening principles that determine the rules to be applied.
- For tactical and economic reasons, the natural terrain should be used for the fortress and artificial aids should be preferred.
- The conquest of a part must not lead to the conquest of the whole fortress.
- The works and fortress sections are arranged in such a way that the missed shots do not necessarily hit others.
- The fortress parts must be separated from each other and arranged in such a way that they can defend each other, whereby the conquest of a part should not offer the attacker any advantage and should put him in an awkward position.
- The fortress defense must be carried out against the two main components of the attack:
- The defensive fire is concentrated against the installation of attack batteries, at this point in time the besiegers cannot exert an appropriate counteraction and the defensive guns can be placed freely on the wall without cover.
- The trench crossing must be fought vigorously, which has to be done by covered fire, against which the enemy can only inadequately take action with his field batteries.
- Creation of adequate shelters for the crew and general needs in order to decisively minimize the effect of the enemy projectiles and the rikoschett shot .
- Increase in mortar batteries in defense.
- In principle, the wall of clothing is hidden from view of the enemy. The free-standing escarpe is preferable, so that its demolition does not go hand in hand with the breaching of the wall.
In the fortress construction of the following 50 years it looks like this: A closed inner enceinte encompasses the city more and more spaciously (possibility of development). Upstream is an external enceinte of detached (advanced), independent works, which keeps the enemy at a distance (→ belt fortress ). These can flank each other. Due to its expansion, the fortress structure enables an entrenched camp, permits external warfare and permits both defensive and offensive use. The result is a paved area that was previously not to be paid for in this size (Koblenz circumference 14 km). The advanced forts receive a three-sided earth wall, the shape of which is adapted to the terrain and the strategic importance. The throat side is usually given a crenellated wall and in the middle a cased, bricked reduit (designed as a multi-storey gun turret) or block house.
These principles are then applied in the German area when building the fortresses Cologne (from 1816), Danzig (from 1818), Erfurt (from 1818), Thorn (from 1818), Minden (from 1827), Posen (from 1829), Germersheim (from 1834), Linz (from 1828), Verona (from 1837), Przemyśl (from 1853), Krakow (from 1849), Komorn (from 1849), Mainz (from 1825), Luxembourg (from 1826), Rastatt (from 1842) and Ulm (from 1843) taken into account.
literature
- Klaus T. Weber: “New Prussian Fortress Manner” - a myth? In: German Society for Fortification Research (ed.): Fortress architecture in the center of Europe (Fortress research; Vol. 3), Verlag Schnell & Steiner, Regensburg 2011, pp. 49–60, ISBN 978-3-7954-2524-1 .
- Klaus T. Weber: The Prussian fortifications of Koblenz (art and cultural studies research; Vol. 1). Publishing house and database for the humanities, Weimar 2003, ISBN 3-89739-340-9 (plus dissertation, University of Mainz 2000).
- Hartwig Neumann: Fortress architecture and fortress construction technology. German defense architecture from the 15th to the 20th Century . Bernard & Graefe Verlag, Bonn 2004, ISBN 3-89996-268-0 (EA Bonn 1988).