The battle of Helmstadt (25 July 1866) saw the Prussians defeat a Bavarian force that was moving south to aid its Federal allies, who suffered a separate defeat of their own a little further to the south-east, at Gerchsheim (Austro-Prussian War of 1866).
At the start of the war the Prussians faced three opponents in western Germany - the Hanoverians in the north, the 8th Federal Corps (Prince Alexander of Hesse) around Frankfurt and the Bavarian Army (Prince Charles of Bavaria), at Bamberg. While the Prussia Army of the Main (General Falckenstein) concentrated on defeating the Hanoverians, the Allies discussed what to do. Eventually they decided to try and unite close to the Hanoverian's original destination, but this plan was foiled, first by the Hanoverian surrender on 29 June and then by rapid Prussian movement. On 3 July the Bavarians ran into the Prussians at Dermbach, at the northern end of the Hohn Rhön Mountains. On 4 July the Prussians won a battle around Dermbach, ending an Allied plan to unite at Fulda. Both Allied forces retreated south. The Bavarians attempted to defend the line of the Saale River, east of the mountains, but the Prussians moved too fast for them, and inflicted two defeats on them on 10 July (Hammelburg and Kissingen). As the Bavarians retreated towards Würzburg, the Prussians turned west to occupy Frankfurt and the area north of the Main. As they crossed the Spessart they defeated part of the 8th Corps at Laufach (13 July), and then captured Aschaffenburg on the Main (14 July).
On 15 July Prince Alexander's corps moved south across the Odenwald. By the end of 16 July were close to Miltenberg, where the Main turns north after flowing west past the southern edge of the Spessart. As the Federal troops moved south, the Prussians were moving west towards Frankfurt, so Prince Alexander was able to rest his men on 17 July. They then turned east, and by 22 July were in a new position on the River Tauber, which flows north into the stretch of the Main south of the Spessart.
Frankfurt fell to the Prussians on 16 July. They then turned south-east to pursue the 8th Corps, which was finally retreating towards the Bavarians. Their route took them around the southern end of the Spessart, moving along the southern side of the Main. This meant that the Allies were finally close enough to coordinate their activities, but they misused this opportunity. Prince Charles wanted to move west to join the 8th Corps and then advance down the Main back towards Frankfurt. Prince Alexander didn't want to retrace his steps, and insisted on a far worse plan for an advance across the Spessart. The Bavarians would north-west from Würzburg towards Lohr, cutting across a northwards loop in the Main. The 8th Corps would move into this same loop from the south, and would cross the Main somewhere to the south of Lohr. Both Allied commanders dismissed the idea that the Prussians might be moving along the line of the Main, and instead expected to find them somewhere in the Spessart, if they advanced at all.
The Prussians of course had taken just the course that the Allies had dismissed. On 16 July Falckenstein occupied Frankfurt, but he was then replaced by General Manteuffel, one of his divisional commanders. Manteuffel visited Frankfurt on 20 July, and then ordered his new army into movement. By 22 July his leading troops were close to Miltenberg, where the Main turns north-west after flowing around the Spessart and begins to flow towards Frankfurt. On 23 July the Prussians defeated the 8th Corps outposts west of the Tauber (combat of Hundheim), and on the following day defeated a possible attempt to hold the line of the river (battles of Tauberbischofsheim and Werbach). The 8th Corps retreated towards the Main around Würzburg, with the intention of seeking safety behind the river.
Early on 24 July, when it became clear that they had misjudged the Prussians Prince Charles cancelled the advance on Lohr, and instead ordered his army to turn back to concentrate around Rossbrunn, west of Würzburg.Stephan's Division had moved west towards Wertheim, to make contact with the 8th Corps. The main body of his division was spread out around Uettingen (west of Rossbrunn), Helmstadt (south-west of Rossbrunn, south of Uettingen) and Holzkirchen, on the road west from Uettingen. He had outposts at Neubrunn (south-west of Helmstadt), Kembach (west of Neubrunn) and Dertingen (west of Holzkirchen).
Prince Leopold's Division was only at Hettstadt, between Rossbrunn and Würzburg, so his movement was fairly simple. Feder's Division took the railway to Zell, on the left bank of the Main north-west of Würzburg, and then followed Prince Leopold (although three battalions remained at Gemünden in case the Prussians were also crossing the Spessart. Hartmann's Division had already reached Markt-Heidenfeld and Lohr, on the Main as it flowed south past the eastern side of the Spessart. They remained in place to guard against the same possible Prussian movement.
When news arrived of the Prussian victories at Tauberbischofsheim and Werbach, Prince Charles decided to move south to aid his allies. Early on 25 July Stephan's Division was ordered to move to Unter-Altertheim, south of Helmstadt. Prince Leopold's Division was to abandon a planned move to Helmstadt, and instead move to Ober-Altertheim, about a mile east of Unter-Altertheim. Feder's Division was to move to Waldbrunn, a couple of miles further to the north-east. At the same time the 8th Corps was retreating towards Gerchsheim, south-east of Ober-Altertheim. The two Allied corps were thus moving back towards each other.
By 10am the Prussians were already across the Tauber. Manteuffel didn't know the Bavarians had moved south, and intended to outflank the 8th Corps' right wing, cutting them off from Würzburg and splitting the Federal army in half. He advanced in three columns. On the left Flies was sent towards where the Bavarians were believed to be, the Prussians not having discovered their recent movements. As a result he wouldn't play a part in the upcoming battles. In the centre Beyer was to advance to Neubrunn, then on to Unter-Altertheim. On the right Goeben was to advance along the high road to Gross Rinderfeld, south-west of Gerchsheim.
Beyer's route east meant that he would inevitably clash with the Bavarians, who were attempting to move south across the same ground.
Beyer set off at about 11am, advancing in two columns. Most of his men started around Werbach. On the right the advance guard and the reserve advanced north towards Böttigheim, along a valley that left the Tauber just north of Werbach. The main body moved down the Tauber to Niklashausen, then turned up a parallel valley.
The advance guard found some Bavarian cavalry at Böttigheim, but they retreated without a fight. The first serious resistance thus came at Neubrunn, which was occupied by the 1st Battalion, 8th Bavarian Regiment, from Stephan's Division.
Both Prussian columns arrived outside Neubrunn at about 1.30. They hadn't expected to encounter the Bavarians, who were believed to be further north, but Beyer decided to attack anyway. A short infantry and artillery attack forced the Bavarians to retreat north towards Helmstadt. The Prussians followed up for a short distance, but General Beyer was now faced with an unexpected problem. His orders were to move east to Unter-Altertheim, but this would leave his left flank exposed to a possible Bavarian attack. He decided to pause at Neubrunn, and wait for news from General Goeben, or further orders from Manteuffel.
The only problem with this plan was that his advanced troops were under constant fire from the Sesselberg, a hill on the road that ran north-east towards Helmstadt. The 20th Regiment was sent forward and soon cleared the Bavarians off the Sesselberg, and they resumed their retreat towards Helmstadt. This advance didn't solve Beyer's problems. The Prussians on the Sesselberg now came under fire from one of Prince Leopold's Division, which was posted on a hill east of Helmstadt.
Beyer was now dragged into a battle with Prince Leopold's Division, which was attempting to advance south from Rossbrunn to Ober-Altertheim. He decided to take Helmstadt. General Glümer attacked north-east from the Sesselberg, and Genearl Woyna attacked advanced north. On the right the fresh 32nd Regiment was ordered to defend a wood against Prince Leopold's troops.
The Bavarians didn't attempt to defend Helmstadt, and instead withdrew north to Uettingen. Beyer sent the Fusiliers of the 20th Regiment to watch the retreating Bavarians, while the rest of the regiment stopped at Helmstadt.
The Prussian 32nd Regiment came up against more serious opposition. The Bavarians attempted to hold the woods on the Altersberg, but they were slowly forced back after the Prussians committed the 39th Fusilier Regiment to the fight at around 5.30pm. The Bavarians retreated east towards Waldbrunn. At around 6pm Prince Leopold, aware that he was unsupported, decided to order a retreat.
Once again Beyer hoped that he had a chance to rest his men, but at this point Stephan's Division reappeared on the scene, coming from Uettingen in the north. Beyer's division was now facing east, towards the retreating troops of Prince Leopold's division, so the new Bavarian assault threatened his left flank.
At first neither commander was entirely sure whose troops he was facing, with both fearing that they might attack their own men. Two Bavarian artillery batteries then opened fire, forcing the infantry on the Prussian left to take shelter in some woods. The Prussian 30th and 70th Regiments turned left to face towards the advancing Bavarians.
The Prussian 20th Regiment took the sting out of the Bavarian attack by advancing though some tall standing corn and catching the Bavarians by surprise. First the Bavarian infantry, and then their artillery, was forced to retreat back north towards Uettingen. The 30th and 70th Regiments then joined the attack, forcing the Bavarian infantry back. Both sides now had artillery in place, the Prussians on the Lange Hohn hills between Uettingen and Helmstadt and Bavarian guns on hills north of Uettingen. In the meantime the two side's infantry clashed in the lower ground between the two sets of hills. The battle finally ended at around 8am, when the Bavarians retreated under cover of darkness.
The Prussians lost 31 dead, 285 wounded and 37 missing at Helmstadt. Bavarian losses were higher, at 43 dead, 408 wounded and 279 prisoners.
On the same day the 8th Corps suffered a defeat at Gerchsheim, which only sped up their retreat towards the Main.
The Bavarians stayed in the field for a little longer, but they suffered another defeat at Rossbrun, north-east of Helmstadt (26 July 1866). By this point the war was clearly coming to an end, as peace negotiations got under way in Austria. News reached the Main front that a formal truce was to come into effect on 2 August. A local ceasefire was agreed, which held until the end of the war. However on 1 August Manteuffel threatened to end the ceasefire unless the Bavarians surrendered Würzburg, and on the following day the Prussians marched into the city.