As a Ravelin (German: Wall Shield ) is called the Fortress being a standalone business , whose job it is to the curtain wall , so the wall between two bastions protect - hence its German name Wall Shield - while their Facen (the enemy side and the front, outer side of a fortress).
Historical development of the ravelin
The Ravelin is the oldest and at the same time most important external structure of the bastionary fortification system. It arose from small foreworks that were supposed to cover the bridge that led over the moat to the city and fortress gates from a direct attack. Its original Italian name “Rivellino” (meaning small river bank or with the usual German expression for it: bridgehead ) comes from this original function of protecting the gate bridge . Therefore, the Ravelin was initially only a small work that was only intended to make access to the bridge in front of the fortress gates more difficult.
When it was recognized in the 16th century that so generally the curtain wall was better protect people began to build and these gradually increase in front of other curtain walls ravelins. However, it was only the German fortress builder Daniel Specklin (1536–1589) who recognized the fundamental importance of the Ravelins (which he still referred to as "single weir" or "Revelin"). He requested that they be made as large as possible so that they could fully cover the curtain wall and the flanks of the bastions, and so that a flanking fire could be placed in front of the bastion tops. In the following period, ravelins can be found in practically all fortresses that were built according to the bastionary fortification system.
In the bastionary fortress system, the Ravelin (almost) always has a roughly triangular floor plan and is therefore either a Flesche (a movement with two faces) or a bezel (a movement with two faces and two flanks). It was always built in the moat of the curtain wall, whereby its walls were always lower than those of the main wall behind it and the adjacent bastion walls. Since the 17th century, its base was always at least wide enough to completely cover the curtain behind it. Usually (but not always) there was another ditch in front of the ravelin as an obstacle to the approach.
First, the Ravelins were built entirely from masonry . From the late 16th century onwards, mainly in northern Europe, people began to build up earth walls, as these absorb the cast-iron cannon balls of the siege artillery better than pure masonry.
The oldest preserved wall shield is in the Italian town of Sarzanello in Liguria and was built in 1497. Originally, it was supposed to protect the gates of a fortress that were connected to them by a bridge or an embankment (as in the Ravelin Peter of the Petersberg Citadel in Erfurt ). Towards the end of the 16th century, people began to build particularly wide ravelins in front of goalless wall sections , from which the entire trench section in front of the bastions could be shot at (as with the Ravelin Anselm of the Erfurt Citadel Petersberg).
Ravelin Anselm of the Petersberg Citadel (built between 1681 and 1700)
One of the oldest surviving ravelins is that of the bastioned Castle Homburg (Saarland). It was built in the last quarter of the 16th century as part of the expansion of the medieval Homburg to a bastioned castle.
Under the impression of the Thirty Years' War , the Zurich Council decided to fortify the city on a large scale according to the most modern knowledge of the time. After a lengthy evaluation of the most varied of fortification systems , Johann Georg Werdmüller's project was no longer built as a raised curtain wall from 1642, but according to the bastionary fortification system and thus partially anticipated the construction method (Vauban fortress) by Sébastien Le Prestre de Vauban (1633–1707). The existing fortifications of Lake Zurich were expanded in 1657 to include the pentagonal Ravelin Kratz in the Limmat (see also Zurich city fortifications ). The bulwark, open on the city side, was connected to the Kratzquartier opposite or the Bauhaus workspace by a footbridge with a drawbridge.
In 1708, under Prince Bishop Johann Philipp von Greiffenclau zu Vollraths, the Ravelin "Teutschland" was built on a square floor plan for the Marienberg Fortress in Würzburg as an outer work in front of the main wall.
- the details are not clearly visible on this picture. The moat is not shown in other pictures showing the siege of Orsoy in 1672.
- Riistow, The Doctrine of the Newer Fortress War, 1860, Vol. 1, p. 251
- Speckle [= Specklin], Architectura von Vestungen…, 1589, 63-65 (reprint 1972); Engels, The New American Cyclopædia, 1858, p. v. Fortification
- Riistow, The Doctrine of the Newer Fortress War, 1860, Vol. 1., pp. 251ff; Zastrow, History of the constant fortification, 1839, pp. 53–77
- Bernhard von Poten : Concise dictionary of the entire military sciences. 1877, sv Ravelin; Riistow: Military concise dictionary. 1858, sv Ravelin
- Stefan Ulrich: The building history of Homburg (Hohenburg) from its foundation to the time of the French Reunion (before 1146 to 1679) ; in: Burgen und Schlösser, H. 2, 2005, pp. 82–92
- Neue Zürcher Zeitung (November 29, 2003): The most beautiful “building district” in Switzerland , accessed on March 8, 2019
- Stefan Kummer : Architecture and fine arts from the beginnings of the Renaissance to the end of the Baroque. In: Ulrich Wagner (Hrsg.): History of the city of Würzburg. 4 volumes; Volume 2: From the Peasants' War in 1525 to the transition to the Kingdom of Bavaria in 1814. Theiss, Stuttgart 2004, ISBN 3-8062-1477-8 , pp. 576–678 and 942–952, here: pp. 633 f.