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PODs of the Thirty Years War XLI

By Alex Richards

Battle of Mergentheim (“Mariendal” in the drawing), or Battle of Herbsthausen, of 1645. Plan of action, French depiction.

The Battle of Freiburg had been a bloody and indecisive affair on the tactical level, but had created the strategic opening the French needed to sweep through Baden and the Palatinate, giving them control over the whole of the Upper Rhine. While Mercy and the Bavarian army had been able to retreat in good order, the swift resolution of the Torstensson War and the disintegration of Gallas’ army in the north meant that for the first time simultaneous thrusts against both Bavaria and the Habsburg Crownlands could be complicated. While Torstensson was to lead the Swedes into Bohemia- as already covered- Turenne prepared to lead the French on a new offensive in Swabia.

The Battle of Herbsthausen

The opening months of 1645 in Swabia had been quiet, with both sides limited to raiding to due to the lack of available troops for large-scale operations. The French needed to rebuild their infantry after the ruinous losses at Freiburg, while Mercy had detached most of his cavalry under Werth to Bohemia to face the Swedes, only 1,500 of which were to return in April. By then the Swedish success at the battle of Jankau was leading Cardinal Mazarin to push for a new offensive in the south, hoping to knock Bavaria out of the war while the Emperor was distracted.

Turenne was thus the first on the offensive, gathering 11,000 men in Speyer and advancing across the Rhine and via the Necker to move into the valley of the river Tauber and enter Franconia. Mercy meanwhile feigned defeatism while gathering his troops, refusing to cross the Danube or meet Turenne in the field for the time being. Tellingly for the later stages of the Thirty Years War, Turenne soon found his strategic positioning dictated by the availability of food and forage supplies rather than military preference. With the valley of the Tauber unable to support even the comparatively small force Turenne had under his command, he relocated in April, billeting his troops in the villages surrounding the town of Mergentheim.

Mercy moved to take advantage, hoping for a second Tuttlingen which would allow the Bavarians to roll back the French advances, or at least comfortably push the field of conflict into the Rhineland once more. Having secured Elector Maximilian I’s permission for the potentially risky manoeuvre, he gathered the 9,650 men and 9 guns that represented essentially the entire Bavarian field army at this point in the town of Feuchtwagen, then force-marched them the 60km to approach Mergentheim on 5th May.

While a patrol under Rheinhold von Rosen succeeded in alerting Turenne to the coming advance in the afternoon, it was too late to avoid the problems of gathering a disparate force together from fatally undermining the French defensive position. Turenne drew up positions on a rise before the village of Herbtshausen, but only had 3,000 infantry and 3,000 cavalry to attempt to hold the position- some of which arrived late to the field of battle. 3,000 more troops and the 6 French guns never made to the battle at all. The battle was short, decisive and never particularly in doubt- the Bavarian guns were able to fire into the French line and the surrounding woods unchallenged, the French infantry routed after the Bavarians began a general advance, and while Turenne was able to rout the Bavarian cavalry by leading a charge of his own troops, he was soon cut off from the army and had to fight his way to the troops covering the French retreat. Mergentheim and the French garrison there surrendered soon afterwards, meaning that for the loss of only 600 men the Bavarians had inflicted 4,400 casualties.

While a clear victory, the battle was not to be a second Tuttlingen. Mercy lacked the troops to do much more than secure the immediate area, and Mazarin swiftly reinforced the French army before the discussions now underway at Westphalia could start to shift against him. It is similarly unlikely that a French victory here would have seen the immediate capitulation of Bavaria- Turenne would have had to wait for the reinforcements required to push forward giving Mercy time to regroup and likely blunt any advance. A Bavarian defeat so soon after the disaster at Jankau could, however, have been the final straw for the Emperor and led to him authorising the negotiating team in Westphalia to make concessions for peace earlier- and perhaps offering greater concessions in the process.

The Battle of Allerheim

Matthäus Merian's depiction of the battle.

As it was, Mazarin was able to send not just 7,000 men in reinforcements but also d’Enghien to lead them, giving them with Turenne at Speyer. Still further, he was briefly joined by 4,000 Swedish troops under Königsmarck and 6,000 under Geyso sent by Amalie Elisabeth of Hesse-Kassel. In response, Archbishop-Elector Ferdinand of Cologne, who had essentially taken charge of the defence of Imperial interests in Westphalia and supporting the Spanish defence of the Moselle valley, sent 4,500 Westphalians south to assist Mercy, giving him 17,000 men against the 23,000 under d’Enghien. However, the battle- which would have potentially seen the presence of just about every significant group still fighting in the Empire save the Emperor himself- failed to materialise. Königsmarck was sent to Saxony to pressure Johann Georg into surrendering before the Imperial army could recover, while Hesse-Kassel was focused chiefly on attacking Hesse-Darmstadt while everyone was distracted. It is easy to see how these differing aims, combined with the difficulties of command structure between nations and d’Enghien’s preference for aggressive frontal attacks could have seen a fractious French-led army essentially breaking apart in the heat of battle, though a decisive victory over the Bavarians may have allowed for an earlier push against them than the historical 1646 campaign.

D’Enghien did, however, retain Geyso and his Hessians as he advanced south, pushing for Franconia and seeking to knock out Bavaria as the Swedes focussed on Saxony and the Emperor. Mercy, ever the master of strategic manoeuvre, moved from fortified position to fortified position, forcing d’Enghien to divert around him time and again. Eventually they ran out of space to continue this at Allerheim- though the battle is also known as the Second battle of Nördlingen thanks to that town being nearby. Mercy deployed in a strong defensive position with his back to the river Wörnitz where the church, cemetery and stronger houses of the village of Allerheim provided the core of a defensive position between two steep hills, the wider Wenneberg to his right, and the Schlossberg, crowned with a ruined castle on the left. These two hills provided elevated positions for some of his guns, while the cavalry were positioned between the town and the hills on either side for ease of movement. D’Enghien, once again overruling his subordinates in deciding to attack, once more favoured a frontal assault, though in this case he had at least learnt enough from Freiburg to feel the need to attack swiftly before the Bavarians could entrench themselves too much. He positioned Geyso, Turenne and the Hessians on his left, Gramont on his right and the majority of the infantry and guns facing the Bavarian centre. Battle commenced with d’Enghien launching an initial assault at 5PM- an unusually late time for the period. As might be expected the fighting was both focused and fiercest in the village of Allerheim itself. D’Enghien led wave after wave of French infantry against the Bavarian positions only to be repulsed by fresh troops led by Mercy. The thatched roofs of the village caught fire forcing the defenders to abandon all but the stone buildings, and smoke spread across the battlefield. In the chaos of the fighting both d’Enghien and Mercy found themselves under direct fire. The former saw two horses killed from underneath him before deflecting a musketball from his breastplate. The latter was less fortunate, taking a direct shot to the head at 6PM and dying instantaneously. The Bavarian army, however, continued to fight on. Further afield Werth routed Gramont, who had assumed that shallow ditch between them was an impregnable line of defence and allowed the Bavarians to come too close to his lines. Werth could potentially have swung round to attack the flank of the French centre here, but with the battlefield possibly obscured with the smoke of guns and burning thatch, his troops spread out chasing down Gramont effectively removing them from the field for the moment. Turenne however had better fortune, attacking up the Wenneberg and then using the fresh Hessians to overwhelm the Bavarian guns. Turenne was then able to attack the rear of the Bavarian centre, and by the time Werth arrived back on the scene the troops there had surrendered. He collected the troops still on the Schlossberg and retreated in good order to nearby Donauwörth. The battle had been another bloody affair- with 4,000 dead on each side, mostly infantry killed in the fighting in Allerheim itself- and inconclusive up until Turenne’s final attack surrounded Allerheim. It was also a fight which d’Enghien was extraordinarily lucky to be able to treat as a victory. Turenne being repulsed from the Wenneberg, Werth managing to keep his troops together in order to attack immediately after routing Gramont, or Mercy not being killed in the fighting and being able to continue to lead the defence in Allerheim could all individually have seen the battle end with the Bavarians in the stronger position. Still further, d’Enghien could easily have been the one to die here instead of Mercy. A second decisive French defeat in their attempts to invade Bavaria would have given significant hope to the Imperial side, as well as preventing Johann Georg of Saxony’s capitulation to Sweden later that year driven as it was more by despair at the prospect of being rescued than the immediate strategic situation. Mercy would, however, have had the same problems following up the battle as d’Enghien had historically. Where Bavaria would have been unable to provide fresh troops in significant numbers, d’Enghien found his requests for reinforcements rebuffed by a Paris aghast at the scale of the losses to the French infantry in Allerheim. He was able to capture nearby Nördlingen and Dinkelsbühl, but failed to repeat the endeavour at Heilbronn, not helped by the fact that he fell ill during the siege here. Leopold Wilhelm of Austria was thus able to march 5,300 troops from Bohemia in early October to face Turenne, taking advantage of the Swedish failure to capture Brünn. In a mirror to the Swedish situation in Bohemia, Turenne was forced to retreat to Alsace, abandoning the towns captured that year and effectively rolling back the frontlines once more. The year could easily have been dismissed as a tactical mirage and a strategic disaster were it not for one thing- Johann Georg, facing Königsmarck ravaging his lands, demoralised by Jankau and with Allerheim ending any hope of Bavaria marching to his aid sued for peace with Sweden. Thus as 1646 dawned, Emperor Ferdinand III had lost one key ally. By the end of the year he was to have lost the other.


Alex Richards is the author of Tippecanoe and Wallace Too, published by SLP


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