The battle of Aschaffenburg (14 July 1866) saw the Prussians gain a foothold on the Main River east of Frankfurt and made it more difficult for the two Federal forces opposing them to join up (Austro-Prussian War of 1866).
At the start of the war the Prussians faced two opponents in south-western Germany, the Federal 8th Corps at Frankfurt and the Bavarian Army at Bamberg. Further north was the Hanoverian Army. If these three forces had been able to unite, then the Prussian Army of the Main would have been rather badly outnumbered, but this never happened. While Prince Alexander of Hesse, commander of the 8th Corps, and Prince Charles of Bavaria, commander of the Bavarian Army, argued about the right way to react, the Prussians, under General Falckenstein, concentrated against the Hanoverians. Although the Hanoverians did win a battle at Langensalza (27 June 1866), they were soon surrounded and surrendered on 29 June.
This meant that the southern Allies' plan to unite around Hersfeld, north of the Hohn Rhön Mountains, was no longer valid. Prince Charles attempted to convince Prince Alexander that their two corps should unite further south, but Prince Alexander insisted on continuing to move north. The two commanders agreed to unite at Fulda, to the north-west of the mountains. However this plan failed to take into account the Prussians, and as the Bavarians attempted to move around the northern end of the mountains they ran into a Prussian force at Dermbach. On the following day the Prussians won two separate engagements near the town (battle of Dermbach, 4 July 1866). The concentration at Fulda was cancelled and the Allies began to retreat back towards their starting points. The Bavarians hoped to defend the line of the River Saale, on the south-eastern side of the mountains, but once again they underestimated the Prussians. The Bavarians expected to be attacked from the north on 11 July at the soonest, but the Prussians crossed the mountains and hit them from the west on 10 July (battles of Kissingen and Hammelburg). The Bavarians retreated east and south in some confusion, but they were saved from further defeats by events elsewhere. It was clear that peace negotiations would soon begin in Austria, and the Prussian leadership wanted to make sure that the area north of the River Main was in their hands when the negotiations ended. Late on 11 July Falckenstein was ordered to turn west, and occupy Frankfurt and the surrounding areas.
This meant that the Prussians would need to cross the Spessart, a range of low wooded mountains south of the Hohn Rhön. The Prussians advanced in two columns. To the south Goeben's and Manteuffel's Divisions advanced west from Lohr to Aschaffenburg. Both places were located on the Main, which swings south in a large loop to pass the Spessart. To the north Beyer's Division followed a road that emerged from the mountains at Hanau, to the north-west of Aschaffenburg.
In theory this left Goeben's Division exposed to an attack by the larger Federal 8th Corps, but Prince Alexander missed his chance. The Bavarian defeats on the Saale helped convince the Prince that union with the Bavarians was more important than defending Frankfurt, and so he prepared to move around the southern end of the Spessart to join up with his allies somewhere near Würzburg. In order to cover this movement the Hessian Brigade was ordered to advance along the road from Aschaffenburg to Lohr, to watch for any Prussian advance. Instead the Hessians became involved in a significant fight at Laufach (13 July 1866), and suffered a heavy defeat. That evening Prince Alexander received fresh orders. The move south-east from Aschaffenburg was cancelled. Instead he was to move south through the Odenwald, south/ south-east of Frankfurt. He was then to turn east to reach Miltenberg on the Main, and then continue east to join up with the Bavarians around Uffenheim, south-east of Würzburg.
Aschaffenburg was defended by the 4th (Combined) Division, made up of one Austrian and one Nassau brigade, commanded by Field Marshal Neipperg. He had some limited support from General Perglas's 3rd Division (Hesse-Darmstadt), but that division had suffered heavy losses at Laufach. Before the fighting began, troops from the Combined Division replaced the Hessians at Goldbach, two miles east of Aschaffenburg.
General Goeben's division resumed its march at around 7.30am on 14 July, again with Wrangel's Brigade in the lead.
In 1866 Aschaffenburg was a small town on the east bank of a curve in the Main, which flowed north-east towards the town, then curved around to flow west away from it towards Frankfurt. A railway ran across the Spessart to Aschaffenburg, following the same valley as the Prussian advance. Goeben advanced with Kummer's Brigade on the left, following the line of the railway, and Kummer's Brigade on the right, on the road for most of the route, although just outside the town the road crossed the railway. Tresckow's cavalry brigade followed close behind.
As the Prussian troops advanced they found Federal troops at Hösbach, and formed up ready for a battle. Instead of attacking, the Federal troops retreated from Hösbach, and then from Goldbach, falling back all the way to Aschaffenburg.
As the Prussians approached the town they came under fire from a well positioned Austrian artillery battery. The Prussian guns couldn't get into a good position for counter battery fire, and the advance was held up for some time. The deadlock was broken when three battalions from the 15th Prussian Regiment captured Damm, just to the north of the town, and captured a nearby hill (topped with a tower surrounded by a wall). The Austrian artillery was now within rifle range, and was forced to retreat.
On the Prussian left the 13th Regiment captured a pheasantry and inflicted heavy casualties on the retreating Austrians. Kummer's 53rd Regiment then pushed into the outskirts of the town, and soon captured the only bridge over the Main. 200 Austrian prisoners were captured by the same troops as they attempted to cross the river by boat.
On the other flank Perglas's battered division withdrew, and retreated towards Seiligenstadt (north-west down the Maine). This forced Neipperg to order a full retreat. Many of his troops were trapped within the town. In addition the Italian troops of the Wernhardt Regiment, who had fought well earlier in the day, now surrendered in large numbers.
News of Goeben's success soon reached the Württemberg Brigade, which had been marching towards the town. The advance was cancelled and the brigade withdrew from danger.
As was so often the case during this campaign, the Federals suffered much higher casualties than the Prussians lost 27 dead, 144 wounded and 9 missing, a total of 180 casualties. The Federals lost 226 dead, 484 wounded and 1,759 prisoners, a total of 2,469 casualties.
The defeat at Aschaffenburg meant that the original route close to the Main was no longer safe. Prince Alexander had to send his troops further west, crossing the Odenwald before they could turn east to begin the journey towards Würzburg. They began to move south on 15 July and were close to Miltenberg by the end of 16 July. After a rest day on 17 July the move east began, and by the end of 22 July the 8th Corps had taken up a new position along the River Tauber, south of the big loop where the Main flows around the Spessart.
This move left Frankfurt undefended and the city fell to the Prussians on 16 July. After a brief pause, in which Falckenstein was replaced by Manteuffel, the Prussians advanced south-east along the Main. They caught up with the slow moving 8th Corps close to the River Tauber, south of the Main. Once again the Allies had underestimated their opponents, and were planning to go back onto the offensive. Once again Prince Alexander's stubbornness meant that the best plan, to unite on the Tauber and advance along the Main, had to be abandoned. Instead the allies agreed to move north, then cross the Spessart themselves to attack the Prussians around Frankfurt. On 23 July the Bavarians began to move north-west from Würzburg towards Lohr on the Main, but on the same day the Prussians defeated the Federal outposts west of the Tauber (combat of Hundsheim). Prince Alexander withdrew to the river, but his attempts to defend it ended in failure (battle of Tauberbischofsheim, 24 July 1866). This defeat forced Prince Charles to abandon the move north, and once again the Allies began to move towards each other. All this meant was that the Prussians were able to defeat both of them on the same day. On 25 July the Bavarians were defeated at Helmstadt while the 8th Corps was defeated further to the south-east, at Gerchsheim. The defeated Allies began to retreat back towards the Main around Würzburg, suffering another defeat at Rossbrun on the way (26 July 1866). By now it was clear that the war was coming to an end. News reached both commanders that a formal truce was to come into effect on 2 August. In the meantime a temporary ceasefire was agreed. On 1 August Manteuffel threatened to bombard Würzburg unless the city surrendered, and on 2 August, just before the formal truce came into effect, the Prussians marched into the city.