Dover Castle Napoleonic Spur Raised Gun Platform - Redan or Ravelin? Kent, UK

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John Latter on July 21, 2011

The Napoleonic structure known as the Redan at the northern end of Dover Castle is an irregular triangle in plan view. The north-eastern face (in shadow on the right) is about 44 yards long, the western face on the far side is about 46 yards along, and the straight-line distance across the sunlit sawtooth-shaped base is about 41 yards.

The last section of the base turns to the right and is out-of-view; its "line of march", however, can be deduced from where the inside perimeter wall of the western edge ends as it drops down on the skyline.

The arrow-shaped Redan, a raised gun platform surrounded by its own moat (ditch), is embedded within the elongated and larger triangle, or "arrow", of the Spur earthwork.

If the same baseline is used for the Spur as for the Redan then the width of the Spur at this point is 80 yards, its north-eastern edge is 115 yards long, and the western edge is 105 yards long (all measurements are approximate!).

The distance from the apex of the Redan to that of the Spur is about 65 yards, note that the two triangles are not perfectly aligned.

Part of the inside of Spur's western perimeter wall can be seen halfway down the left-hand side of the photo.

The Spur, originally teardrop-shaped, was constructed after the 1216 Great Siege of Dover Castle in the First Barons War.

During the siege, which broke off and then resumed briefly in 1217 when a trebuchet catapult was used (Malvoisin, or "Bad Neighbour"), the engineers of the Dauphin (Prince Louis, later Louis VIII of France) so damaged the eastern gate tower of the North Entrance by mining that Hubert de Burgh (Constable of Dover Castle under King John and Henry III) subsequently sealed the gateway.

The Norfolk Towers replaced the Northern Entrance (or Northgate) and new gateways were made at Fitzwilliam’s Gate (in the east) and at Constable’s Tower (in the west). A round (or cylindrical) tower called St John’s Tower was also built in the moat in front of the Norfolk Towers.

The Spur was connected to St John's Tower (out-of-shot to the left) and then to the castle interior by an underground passageway and tunnel that passed under the Norfolk Towers to surface beneath the keyhole-shaped tower at the end of the causeway in front of the North Barbican, or King's Gate Barbican.

The Spur was reshaped during the Napoleonic Wars and the Redan added.

In the bottom left-hand corner of the photo is the two-storey Spur Caponier (Spur Caponnier), also Napoleonic, that crosses the outer moat of Dover Castle to connect the Redan to St John’s Tower. This is the only tower sited in the outer moat, and for the purpose off these webpages, marks the point where the northern part of the Eastern Outer Curtain Wall (this side of the caponier) becomes the northern part of the Western Outer Curtain Wall (far side).

The roof of the Spur Caponier's upper level is a two-stage affair with a round opening in the gable face (looks like a black oval in the photo). This is a light shaft that throws a pool of light onto the tunnel floor just before it branches into three other tunnels inside the Redan. Anyone trying to enter the Spur Caponier from these tunnels has to pass through the pool of light where they can be seen by guards from behind their protected positions.

Not shown in this photo are either of the sub-caponiers that lie between the Spur Caponier and the Spur gunrooms whose field of fire is along the moats on each side of the redan: the grass- and ivy-covered western gunroom lies just beyond the foreground fencing, immediately below the redan and to the right of the Spur Caponier's upper-roof level.

The photo was taken at 11.25 am on Friday, 13th of May, 2011. On the distant skyline at top-right are Plum Pudding Hill and the Hougham Television Transmitter (Hougham TV Mast; Hougham Radio Mast, VHF and UHF).

The Napoleonic Dover Castle (1)

A present-day account:

Massive rebuilding took place at the end of the eighteenth century during the Napoleonic Wars with France. Colonel William Twiss, the Commanding Engineer of the Southern District, as part of his brief to improve the town's defences, completed the remodelling of the outer defences of Dover Castle adding the Horseshoe Bastion, Hudson Bastion, East Arrow Bastion, and East Demi-Bastion to provide extra gun positions on the eastern side, and constructing the Constable's Bastion (Constable’s Barbican) for additional protection on the west.

Twiss further strengthened the Spur (remodelling its shape) at the northern end of the castle, adding a redan, or raised gun platform. By taking the roof off the Keep (or "Great Tower") and replacing it with massive brick vaults he was able to mount heavy artillery on the top. Twiss also constructed Canon’s Gateway (alt. Canons Gateway) to link the defences of the castle with those of the town.

A Victorian account (July, 1899) (2):

In 1779, England being at war, not only with her American colonies, but also with France and Spain, fears were entertained of an invasion, and Dover was hastily placed in an extra state of defence. In the summer of 1779 the first earthwork was thrown up on the Western Heights...

...Considerable repairs were made in the Castle in 1793, and in the next year further accommodation was found for troops in the old church in the Castle (St Mary-in-Castro). In 1794 Guildford Shaft (behind Henry VIII's Mote’s Bulwark) was commenced and finished in 1795. The Castle was at that time supposed to contain accommodation for 724 men. The modern alterations visible in the Debtors' Prison (Fulbert Tower) were made in the same year, and the present gateway and caponiere at Canon’s Gate were constructed. The Spur was also extensively altered, and its present form is much what it was in 1795.

Hudson's Bastion, the east demi-bastion and other work's on the east front, including the caponieres and galleries, were completed about the same time. The cliff casemates (the "Secret Wartime Tunnels") were also finished at this date, and the C.R.E. (Commander Royal Engineers: Twiss) reported that they "exceeded his expectations both in point of solidity and dryness"...

...In 1800 the Castle was armed with 211 pieces of ordnance, which included twenty-eight mortars, four ten-inch howitzers and one eight-inch howitzer, forty-four carronades, ten of which were sixty-eight pounds; seventy-four guns, ten amusettes and fifty wall pieces.

In 1802 the bomb-proof guardroom, passages and hanging doors, with "a proper drawbridge" in the Spur, were constructed, and the ravelin cut to its present slope.

Ravelin or Redan?

The List of established Military Terms (3) states:

Ravelin: a triangular fortification, detached outwork in front of the bastions (in this case, the Norfolk Towers).

Redan: a V-shaped salient angle toward an expected attack. It can be made from earthworks or other material.

The Ravelin (4)

A ravelin is a triangular fortification or detached outwork, located in front of the innerworks of a fortress (the curtain walls and bastions). Originally called a demi-lune, after the lunette, the ravelin is placed outside a castle and opposite a fortification curtain.

The edges of the ravelin are placed so that the guns there can sweep fire upon the attacking troops as they approach the curtain. The wall facing the inner fortifications is low and designed so that it will not provide shelter to attacking forces in case the ravelin is overtaken by the attackers or abandoned by the defenders (a similar reasoning is used to explain a feature of Avranches Tower for Crossbows).

The word appears in the Major-General's Song from the comic opera The Pirates of Penzance, by Gilbert & Sullivan, in which General Stanley sings, "In fact, when I know what is meant by mamelon and ravelin..."

Excerpt from a Military Dictionary published in 1802 (5):

RAVELINS, in fortification, are works raised on the counterscarp (outer moat wall) (6) before the curtain of the place, and serve to cover the gates of a town, and the bridges. They consist of two faces, forming a salient angle, and are defended by the faces of the neighbouring bastions. They are the most in use of all out-works, and are by the soldiers most commonly called half moons, or demi Iunes. They should be lower than the works of the place, that they may be under the fire of the besieged. Their parapets, as those of all out-works, should be cannon-proof; that is, about 18 feet thick.

The Redan (7)

Redan (a French word for "projection", "salient") is a term related to fortifications. It is a work in a V-shaped salient angle toward an expected attack. It can be made from earthworks or other material.

The redan developed from the lunette, originally a half-moon-shaped outwork; with shorter flanks it became a redan.

The Russians used redans on their left at the Battle of Borodino against Napoleon. A small redan whose faces make an obtuse angle with a vertex towards enemy is called flèche, an arrow in French. The Bagration flèches were three redans backwards in echelon. The Shevardino Redoubt (another redan) was erected as an early warning post a mile in front of the Bagration flèches.

Excerpt from a Military Dictionary published in 1802 (5):

REDANS, in field fortification, are a kind of indented works, lines, or faces forming sallying and re-entering angles, flanking one another; generally constructed on the sides of a river which runs through a garrison town. They were used before bastions were invented, and are by some thought preferable to them. They are likewise called Ouvrages á scie (french: "Saw works"), from their resemblance to a saw.

Ravelin or Redan? - Comment

I'm not a local historian, military historian, or any other kind of historian. On the basis of a couple of hours internet research, however, I do feel that the 1899 source quoted may be right in terming the raised gun platform at the northern end of Dover Castle, a ravelin.

Certainly, the baseline of the Spur platform has a distinct saw-like shape, but this is an internal charctersitic, perculiar to "local implementation", and not part of the overall pattern of defence directly presented to the field: my interpretation of the 1802 dictionary is that one redan is a saw-tooth, but when "flanking one another", they resemble saw-teeth.

A redan can be part of a curtain wall or "an early warning post a mile in front" of the main fortifications. Ravelins, on the other hand, "are works raised on the counterscarp", which is exactly where the Spur gun platform is. Further to this, a Croatian description of a ravelin states:

Revelin ili ravelin (tal. rivelino; franc. ravelin) u fortifikacijskom graditeljstvu označava vrstu utvrde postavljene da brani njene najslabije točke ili pojedina vrata. Ako se nalazi pred vratima utvrde, revelin je najčešće povezan s njom mostom.

Which translates as:

Revelin or Ravelin (Italian rivelino; french Ravelin) in construction means a type of fortification works set to defend its weakest point, or single door (gateway or entrance: as stated above, the Norfolk Towers stand where Northgate used to be). If it is at the entrance of the fort, revelin is most often associated with it by a bridge.

A bridge would be needed for water-filled moats. Those of Dover Castle are dry and so the Spur Caponier link to St John's Tower provides this optional "bridge" function.

One of the sources quoted states that the wall of a ravelin facing the inner fortifications must be "low", which again is the case for the Spur platform, especially when compared to the height of the two flanking sides of the "arrow".

The 1995 book, "English Castles: A Guide by Counties" contains an undated plan of Dover Castle reproduced by permission of English Heritage. The raised gun platform on the Spur has the number 6 beside it. In the key to the drawing it reads, "6 Ravelin", and not "6 Redan".

It would be interesting to find out exactly when and why the change from ravelin to redan was made!

(1) Wikipedia entry for Dover Castle (Abridged)

(2) The History of the Castle, Town and Port of Dover by Reverend S. P. H. Statham, Rector of St Mary-in-the-Castle (Longmans, Green, and Co., 1899).

(3) List of established Military Terms

(4) Wikipedia entry for Ravelin

(5) A new and enlarged military dictionary, or, Alphabetical explanation of technical terms, by Charles James (London, 1802).

Also see:

A military dictionary, or, Explanation of the several systems of discipline of different kind of troops (etc.), by William Duane (Philadelphia, 1810)

(6) Outer moat embankment, or earthwork: A scarp and a counterscarp are the inner and outer sides of a ditch used in fortifications. In permanent fortifications the scarp and counterscarp may be encased in stone. In less permanent fortifications, the counterscarp may be lined with paling fence set at an angle so as to give no cover to the attackers but to make advancing and retreating more difficult. See Profile of the European fortress wall from the 16th century.

(7) Wikipedia entry for Redan

(8) English Castles: A Guide by Counties by Adrian Pettifer (1995; 2002 edition)

Click to see all photos of Dover Castle, a Dover English Heritage site and a Grade I Dover Listed Building.

A British Army Royal Artillery (Garrison Artillery) and Dover history photo.

John Latter / Jorolat

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Photo details

  • Uploaded on July 20, 2011
  • © All Rights Reserved
    by John Latter
    • Camera: PENTAX Corporation PENTAX K100D
    • Taken on 2011/05/13 11:24:59
    • Exposure: 0.004s (1/250)
    • Focal Length: 20.00mm
    • F/Stop: f/11.000
    • ISO Speed: ISO200
    • Exposure Bias: 0.00 EV
    • No flash