Once the Aulic Council refused Charles's plans,
Latour engaged the main French force at Kehl and Charles entrusted to Karl Aloys zu Fürstenberg the command of the siege force at Hüningen. The process of laying siege in the eighteenth century was complicated. Most commonly, armies established positions around a city and waited for the surrender of those inside: if patience failed, they bribed or coerced someone inside to betray the fortification. An attacker, aware of a prolonged siege's great cost in time, money and lives, might offer generous terms to a defender who surrendered quickly. The defending troops would be allowed to march away unharmed, often retaining their weapons. As a siege progressed, however, the defender's position became more precarious. The surrounding army would build
earthworks in a line of
circumvallation to completely encircle their target, preventing food, water, and other supplies from reaching the besieged city. This was followed by the construction of a line of
contravallation, especially if the besieged city had a nearby field army; the line of contravallation protected the besiegers. Generally, time was on the side of the defenders; most armies could not afford to wait out the prosecution of a siege, especially of a well-fortified, well-provisioned city. Until the invention of
gunpowder-based weapons (and the resulting higher-velocity projectiles), the balance of power and logistics definitely favored the defender. With the introduction of large-caliber
mortars and
howitzers (in modern times), the traditional methods of defense became less effective against a determined siege, although many of the
trace italienne fortresses presented a formidable challenge well into the twentieth century.
Description of the fortifications The principal bridge crossing the main part of the river began approximately 400
paces above the point at which the
Kinzig river joined the Rhine. On one side of the confluence lay the hamlet of Auenheim; on the other the village of Neumuhl. The fortress stood between the bridge over the Rhine and the Kinzig. It was shaped as a
polygon, approximately in length, and two of its sides faced the Rhine. The main wall was approximately high. Below two
bastions,
casemates, or fortified gun emplacements of long and wide, provided
enfilade coverage. Behind these lay two other polygons, close the river, which held the magazines: these were high, long and wide. All walls were thick enough to repel most cannon fire. The inner spaces included a section of barracks that cold hold up to 1500 men; indeed, in an earlier bombardment in the hostilities in
September 1796, the barracks, gun emplacements, and walls had withstood a lengthy Austrian barrage. The fortress had stone and mortar
ravelins and each bastion had its own
hornwork; the hornwork between the Rhine and the Kinzig was approximately in length. The hornworks themselves were faced with stone and mortar and had their own ravelines, a covered communication ditch, and an earthen
glacis. The village of Kehl stood on one of the hornworks, built along a single long street. At one end lay the Commandant's Bridge, which crosses the "old water", a subsidiary channel approximately wide, separated from the main channel of the Rhine. Beside the old water, stood the Kehl church, graveyard, and portions of the hornwork, including an earthen dam that followed the shoreline of the river. The fortified wall by the churchyard, capped by a breastwork, had its own
moat; the breast work had room for at least four cannons and 150-200 troops. This entire installation, called the churchyard redoubt, approximately wide, dominated the vicinity. As the Rhine passed the church, it made a sharp curve; this curve and the water where it and the old water rejoin, created a small island known as the Marlener Island. In dry weather, it was more of a
peninsula than an island; the exposed ground was called the
Kehler Rheinkopf (Kehl's Rhine head, or bald head). The island was thick with bushes and shrubbery. Beside this lay a larger island, known as the
Erlenkopf (Erlen head), which supported a battery of artillery (known as Battery 2). The battery was protected only by posts, or palisades, connected to the mainland by a light wood bridge guarded by infantry. The river by the bridge was approximately wide, and by the exposed islands were about wide. In the other direction, between Kehl and the Schutter, which lay downstream, the fortifications were equally secured. The redoubt there held about 8 cannons and 400 men, and covered the street between the hamlet of Auenheim and Kehl.
Conduct of the siege at Kehl Realizing that the siege was imminent, the French had destroyed most of the village of Kehl on 26 October, as the Battle of Schliengen concluded and Moreau's army withdrew toward Hüningen. Only the ruined walls of the church and post house remained. The French maintained control of the three main islands surrounding the Kehl crossings:
Isle de Estacade, Isle de Escargots, and
Isle de Ehrlin. Their control of these provided vital positions from which the French established their operations. The islands were connected to Kehl and to each other through a series of flying bridges (pontoon bridges); troops could also be moved by boat if necessary. On 26 October, Baillet de Latour immediately lay the groundwork for a lengthy siege by ordering the construction of extensive earthworks around the bridgehead. The lines of contravallation (the trenches nearest to the French position) included a series of redoubts connected by trenches. Initially, the French considered these to be purely defensive and they were inclined to ignore the industrious Austrian diggers and focus instead on their own fortifications, which were sketchy and relied upon palisades unprotected by dirt; these could not withstand a vigorous attack until strengthened. After several days of strengthening their outer works by 30 October, several artillery pieces were brought up to augment the outer defense. In addition, released from the main army after the Battle of Schliengen, General Dessaix arrived to command the fortress and augment the garrison with his troops. Subsequently, French reconstruction of the fortress and its defensive lines increased. Several minor sorties against the Austrian lines resulted. On 14 November 1796, Dominique Vandamme, commanding a column of Dessaix's force, directed a small group of skirmishers and
hussars to attack the most forward of the Austrian posts. This successful sortie took eighty Austrian prisoners. On 21 November, while the Austrians constructed their trenches on the right bank of the Kinzig, the French planned for a considerable sortie against the lines of contravallation between the Kinzig and the Rhine.
Action of 22 November At daybreak on 22 November, 16,000 infantry and 3000–4000 cavalry moved against the combined Austrian and Württemberg positions between the Kinzig and the Rhine. The French infantry departed from the small island of Erlen, in the Rhine, and from the left of the entrenchment camp. The first column forced the first two Imperial redoubts. Another penetrated the earthen works near the center and carried the village of Sundheim and the two redoubts that ran contiguously to the village. Three other redoubts between the two were not carried, though, and the Austrians sallied out of these fortifications and fell upon the French. This action was the principal assault on the Austrian/Imperial line and apparently took the besiegers by surprise. Latour and the archduke personally moved to the gap the French created, pulling six battalions of armed workmen and all the Austrian troops after them. The French immediately ran into problems. Infantry intended to support the first wave did not arrive in time. The cavalry could not deploy properly, due to the marshy ground and close quarters. After four hours, the entire French sortie party withdrew, taking 700 prisoners, seven pieces of cannon, and two howitzers. The want of horses prevented them from taking another 15 pieces of cannon, which they
spiked. According to French accounts, thick fog favored the Imperial action, because it prevented the French from reconnoitering. Furthermore, as Moreau reported later, the humidity on the ground impeded the march of their columns, although it is unclear how the fog impeded only French visual reconnaissance and march but not the Austrian's. Regardless, fighting was heavy. General Moreau himself was wounded in the head and his
aide-de-camp Lélée was badly wounded. General Desaix's horse was killed under him, and he received a contusion in his leg, and General Latour's horse was also shot from under him. This action convinced the French that the Austrian and Imperial forces were too numerous and too well-established for them to shake. The French instead focused their efforts on reinforcing their palisades, strengthening batteries, and developing the redoubts and earthen works.
Expansion of the siege Much of the Kehl fortification was built on old ruins. In particular, the oldest of the bridges, which had been largely destroyed earlier in the century, This was an ancient bridge of piles that had been largely destroyed earlier in the century, but which the French had been reconstructing. Where the old stakes remained, the French rebuilt the bridge; where the stakes were missing, they filled in gaps with pontoon spans resting on boats. By 28 November, the Austrians had constructed enough parallels and batteries to fire upon the oldest of the bridges crossing the river. The bridge was entirely demolished; the French repaired it; the Austrians demolished it again. It lay so directly in the line of fire of one of the batteries that it was an easy target. The French could not keep it intact three days straight and furthermore, its wreckage threatened a pontoon bridge immediately downstream. This gave Austrian marksmen close access to the bridges, where they could pick off French defenders with musket fire. It also allowed
sappers to tunnel under the bridgehead walls and engineers to establish artillery batteries that could fire at closer range to the walls. They built some new trenches on the left of the
Schutter stream, by the entrance to the old village of Kehl. Similarly, the French had made several night sorties on the works of the besiegers. In these forays, they would chase the diggers out of the lines, but the Austrian reserves always recovered the works before the French could capture any cannons or destroy the construction. Consequently, every day, the Austrians expanded their works and erected new batteries. The Austrians took the Ehrlinrhin, a large island on which several of the French reserve units had been positioned. General Lecourbe removed one of the flying bridges to cut off all hope of a (French) retreat, grabbed a standard and rallied a battalion to advance against the Austrians, repulsing them as far as their trenches. Lecourbe's quick thinking preserved half of the island for the French. In the following days, the Austrians incorporated the newly acquired territory into their massive lines and batteries. The opened trenches on the left (south) of the Schutter) at the entrance to the old village of Kehl; within the week, the Austrian batteries connected the ruins at Kehl with the left flank of the contravallation, and linked the entire line to one of the Rhine islands, now exposed by receding water. The lines of contravallation, formed of several redoubts, were joined by entrenchments that entirely encircled Kehl and access to the bridges. These began at a dyke near Auenheim, traversed the route to Rastadt and Offenburg, the course of the Kintzig and the Schutter rivers, encircled the village of Sundheim, and finished at the
Bonnet de Prétre. The Austrian troops on the island could cover the left flank and the entire besieging army was covered by considerable entrenchments on the Islands in the Kinzig. By the end of the week, the Austrian and Imperial defenses were connected in a grand parallel and a series of batteries in a semicircle around the village. The Austrians took the ruins of the church and the post house by bringing up artillery and bombarding the positions; this allowed them to complete the lines of contravallation. According to spies and deserters, the Archduke himself had been exhorting and cajoling his troops to lift their spirits, "prepared his troops by harangues and presents," Moreau reported. On 1 January, after a lengthy salvo, 12 Imperial battalions attacked the outer redoubt and the right wing of the French entrenchment, drove the French out, and immediately took possession of the earthen works and six pieces of artillery. French reserves had not been able to traverse the Rhine in sufficient time; boats intended to transport such troops had been damaged by the lengthy cannon fire. The connecting bridges, which had also been damaged, were repaired quickly, but by the time these repairs had been made, the Austrians were deeply entrenched in their new positions and the French could not force them out. Even miners, who had dug under the trenches, were unable to blow up the redoubt.
Surrender Day-by-day, over time, the Austrians increased pressure on the French, who hampered by the lack of bridges or appropriate transport, could not bring up enough reserves to preserve the lost ground. Boats were stove by fire of the cannon; by the time bridges were repaired and sufficient reserves could be moved, the Austrians were entrenched, and had brought up their artillery. The Austrians continued to advance their earth works, and perfect their batteries. At 10:00 on 9 January the French general Desaix proposed the evacuation to General Latour and they agreed that the Austrians would enter Kehl the next day, on 10 January (21
Nivôse) at 16:00. The French instantly repaired the bridge, rendered passable by 14:00, which gave them more than 24 hours to evacuate everything of value and to raze everything else. By the time Latour took possession of the fortress, nothing remained of any use: all palisades, ammunition, even the carriages of the bombs and howitzers, had been evacuated. The French ensured that nothing remained behind that could be used by the Austrian/Imperial army; even the fortress itself was but earth and ruins. The siege concluded 115 days after its investment, and following 50 days of open (digging) trenches, the point at which active fighting began. == Aftermath ==