The battle of Diersheim (20-21 April 1797) was a major French victory won by General Moreau on the Upper Rhine that came two days after Napoleon had successfully negotiated the Preliminary Peace of Leoben, which ended hostilities between France and the Austrian Empire. The Rhine front was something of a backwater in the first few months of 1797, with most attention was focused on Napoleon in Italy, but in March, as Napoleon prepared to cross the Alps into Austria, the French directory decided to launch joint offensives on the Rhine to prevent the Austrians from moving reinforcements east to defend Vienna. General Hoche, with the Army of the Sambre-and-Meuse and General Moreau, with the Army of the Rhine-and-Moselle, were to cross the Rhine on the same day. As in 1796 the two armies were not ordered to cooperate with each other, but unlike in 1796 they were no longer faced by the Archduke Charles, who had been moved to Italy to face Napoleon.
The Archduke had been replaced by General Latour, who in obedience to orders from Vienna had spread his army evenly along the line of the Rhine from Dusseldorf down to Basle. When the French attacks were launched Latour was based around Mannheim, and so was in the wrong place to deal with either attack. Instead Moreau would be opposed by General Anton Sztaray Graf von Nagy-Mihaly.
Moreau decided to cross the Rhine from Gambsheim, to the north of Strasbourg, and close to the point where the River Ill flows into the Rhine. He hoped to gather boats in secret on the Ill, take advantage of the cover provided by a dam near the mouth of the Ill to load the boats in secret, and cross the Rhine on the night of 19-20 April. The troops arrived on time, reaching their embarkation points close to Kilstett, but as the night wore on it became clear that something had gone run further up the river. Not one of the boats had arrived by two in the morning. Two hours later fourteen had turned up, and an hour later twenty-five of forty boats available had arrived.
The problem was caused by low water in the Ill, which caused some of the boats to run aground. The situation was so worrying that Moreau went up the Ill in person to find the boats carrying the army's supplies, even wading up to his waist into the water in an attempt to help push the trapped boats off a gravel bank. When this failed he ordered three companies of infantry to carry the supplies to the embarkation point, but by the time they arrived the sun had risen, and the Austrians could see what was happening.
Moreau decided to attempt to cross the river in daylight. He knew that if he waited until the following night the Austrians would bring reinforcements down from Mannheim, and the landing would probably fail. His one advantage was that the Austrians were distracted by a of a series of French feints, in this case where French troops had actually reached an island connected to the east bank of the Rhine by a ford, and so failed to concentrate their troops opposite the Ill.
Moreau had enough boats to carry 1,500 men. He decided to make his crossing in two waves. The first wave was to land at two points. Generals Duhesme and Vandamme, with a battalion from the 76th demi-brigade and part of the 100th demi-brigade, were to land close to Freistett. General Davoust, with one battalion from the 31st demi-brigade and one from the 16th légère was to land on the island of Stein-Werth, just to the right of Freistett, where the Austrians had an artillery battery. Once the first wave had landed the boats were to return to the west bank and collect General Jordy, with the rest of the 100th demi-brigade, the16th légère and the 31st demi-brigade, was to land on an island separated from Diersheim by some fords and by a narrow bridge suitable for infantry.
The first wave set off at six, and the plan almost immediately went wrong. The Austrian guns opened fire, and to avoid being sunk the boatmen were forced to abandon the landings around Freistett and instead land on the island close to Diersheim.
This island was defended by 300 Croats from Michalowitz's irregular forces. They retreated across the ford and took up a position behind some construction timber that was stacked around a nearby toll hut. The grenadiers from the 76th and 100th demi-brigades attacked their position, and were able to force the Croats to retreat at the point of the bayonet.
For the rest of the day fighting raged around Diersheim which changed hands seven times. While the French second wave was being shipped over, Duhesme, with the 76th demi-brigade, captured the village for the first time, forcing the Austrians to evacuate Stein-Werth. The Austrians then launched a counterattack which retook the village. Duhesme was shot in the hand while attempting to rally his men. Vandamme then arrived with the 100th demi-brigade and took the village for the second time. Once again the Austrians recaptured the village, only to be driven out by Davoust with the 31st demi-brigade and part of the 16th. The French lines then stabilised for some time. Their centre was in Diersheim, their right in Hanua and their left rested on the dikes by the Rhine.
At eleven the Austrians launched their last attack of the morning. By then the French had managed to land three small guns on the east bank, but that wasn't enough to prevent the Austrians from once again capturing Diersheim. This time it was Desaix, with the 17th demi-brigade and a battalion from the 109th who restored the situation and recaptured the village.
After the failure of this attack the Austrians remained on the defensive until the evening, while reinforcements arrived from the fortified camp at Kehl. The Austrian line ran from Honau east to Linx, then north along the Hochenbach stream up to Freistett, effectively pinning the French into their bridgehead.
At two in the afternoon the French completed a flying bridge that crossed the Rhine to the island at Diersheim. By the time the Austrians made their next attack the French had moved more artillery and 400 cavalry across the river
Sztaray decided to make one final attempt to push the French off the east bank of the Rhine in the evening of 20 April, before they could bring even more men across the river. The attack began with an artillery bombardment that dismounted most of the French guns and set Diersheim on fire. The Austrians then forced the French infantry to retreat from the village, capturing General Jordy during the fighting. On the French right General Davoust captured Honau, causing Sztaray to delay the advance from Diersheim. This gave the French time to rally, and they forced the Austrians out of Diersheim, capturing the village for the fourth and final time of the day.
At six in the evening on 20 April the French began to build their bridge of boats across the Rhine, and it was complete by midnight. Overnight Moreau moved his right wing, the cavalry from the centre and the reserve cavalry across the river, and by six General Lecourbe's division was about to cross the bridge.
Sztaray had also received reinforcements overnight, and he now had 16 infantry battalions, 20 cavalry squadrons and 25 guns around Diersheim. He didn't realise that the French had completed their bridge of boats, and so decided to launch a fresh attack early in the morning of 21 April.
Moreau was also planning to attack that morning. Dufour was to attack on the right, between Honau and Diersheim. Vandamme was to attack from Diersheim and Lecourbe, once he had crossed the river, was to take up a position on the left.
The Austrians moved first. At six in the morning they began a fierce bombardment of Diersheim, while columns advanced towards that village and towards Honau. The Austrian attack came close to success. Many of the French troops in Diersheim fled from the artillery bombardment, and attempted to cross the bridge of boats back to the west bank of the Rhine. They were stopped by General Lacourbe and the grenadiers of the 84th demi-brigade, who forced the leading fugitives off the bridge into the Rhine at bayonet point, and then advanced across the bridge in a solid block, preventing anyone from passing.
This was the turning point of the battle. Moreau had managed to prevent a total disaster using his reserves (the 3rd légère, 2nd cavalry, 4th dragoons and a squadron from the 9th hussars). He was then reinforced by seven squadrons of heavy cavalry, and managed to push the Austrian back out of Diersheim yet again.
The fighting around Diersheim had been intense. Moreau and Vandamme had both had horses shot under them, while on the Austrian side General Immen and Sztaray were both wounded while trying to reform their troops.
After the failure of this attack Sztaray decided to retreat back towards the Black Forest, to protect the route along the Kinzig valley to the upper Danube, where the French had campaigned in the previous year. Just as the Austrians were beginning to withdraw, Moreau launched his own attack. The French caught up with the Austrian Rearguard (Alton's regiment, Infantry Regiment No.15) at Griesheim, just to the north-west of Offenburg, where the Kinzig enters the mountains, and quickly dispersed it. This threatened to turn the orderly Austrian retreat into something of a rout. General O'Reilly attempted to organise an rearguard between Bühl and Offenburg, but was captured by the French, and by the end of the day Vandamme had reached Gengenbach, five miles up the Kinzig valley.
On the afternoon of 21 April the French reoccupied the fortified camp at Kehl, opposite Strasburg, the site of a long siege over the previous winter. On the following day they advanced east, to Renchen, and on 23 April Moreau turned north, expecting to fight General Latour, who was finally approaching from the north at the head of 15,000 infantry and 3,000 cavalry. This was not to be. Five days early Napoleon had signed the Preliminary Peace of Leoben. The news reached Latour first, and as the French advanced towards the Austrian lines they were greeted by a Parlimentaire, who informed them of the peace. The French withdrew back to their starting point, and the fighting on the Rhine front came to an end.
The French victory at Diersheim made no contribution to the Austrian decision to make peace at Leoben, but combined with the victory two days earlier at Neuwied it did help Napoleon in the negotiations that eventually led to the Peace of Campo Formio. His achievement at Diersheim did make Moreau just as famous as Napoleon, and gave him the confidence and the reputation to challenge the First Consul's first plans during the War of the Second Coalition, but that confidence also played a part in his slow estrangement from Napoleon.