As the Brux campaign unfolded in the west, Schlesien Armee continued siege operations against Königgrätz, bombarding the fortress with its dedicated battalion of 24 siege guns and numerous field cannon. By the end of September, a sizable portion of the walls have been effectively reduced, allowing Schwerin to assault the fortress at the start of October. The attack is brief and bloody, and Schwerin's infantry soon makes their way inside the fortress, compelling the remaining defenders to surrender. Alongside the fortress itself, 44 guns of the defensive battery and a sizable amount of supplies are also captured.
Scouts from Gessler's cavalry corps, arriving in Jungbunzlau on the opposite bank of the Elbe from Prague, report that there are no Austrian field units near Prague itself. Acting on this intelligence, Gessler and Wedell's columns begin crossing the river towards Prague, where they can either lay siege to the fortress or cut off the Austrian army opposing Frederick. Meanwhile, the Elbe Armee takes up defensive positions in Lobositz as it continues to recover from the Battle of Brux.
These are the
third and
fourth mistakes of the Kingdom of Prussia.
Gessler's cavalry corps, moving faster than Wedell's column, crosses the Elbe with no initial opposition. However, a previously unspotted army of 30,000 Austrians under Aeneas Piccolomini moves into the province at the same time, soundly defeating Gessler and forcing his remaining forces back across the river while distance and poor organization leave Wedell's forces out of reach.
Meanwhile, the main Austrian force in Brux has split. The majority of the army appears to retreat back to Prague, where they come across the now isolated forces of Johann von Wedell and crush it, forcing the column to retreat across the Elbe in disarray as well.
More disastrously, the remaining Austrian force in Brux, comprising the First Line commanded by Joseph Lucchese, bypasses Elbe Armee and enter Dippoldiswalde, which in a fit of idiocy the Prussian army has neglected to reinforce after Moritz von Anhalt-Dessau left his position to join the Battle of Brux, completely unopposed. Lucchese then moves on to Pirna, where he engages Prince Wilhelm outside the walls of the fortified camp. Outnumbered two to one and without support, Wilhelm retreats back to Dresden after a brief engagement, allowing the Austrians to link up with the Saxon army and effectively breaking the siege.
It is at this point that Prussian army's command staff collectively punched itself in the face and began looking at how to put the situation back in its favour. It is nearly certain that the enemy expects Elbe Armee to pursue the Austrian army back to Pirna, where together with the Saxon army it can take up defensive positions in the mountainous terrain and defeat it, so this course of action must be avoided. Instead, with Schwerin's army now free to pursue further operations after the successful capture of Königgrätz, a plan is put in motion to attack Prague, hopefully catching the Austrians by surprise and allowing the defeat of the now joined armies of Maximilian Browne and Piccolomini.
The operation proceeds exactly as predicted. The Austrians and Saxons, as expected, combine their forces outside of Pirna and prepare for attack, but the only move made by the Prussian army in that direction is to leave Hans von Zieten's Hussar Brigade in Dippoldiswalde to watch the Austro-Saxon army and cut it off from supplies.
Elbe Armee and Schlesien Armee both head towards their objective, and on October 28th the Battle of Prague begins as Frederick's forces begin crossing the Moldau river and are engaged by Browne's army. An hour later, Schwerin joins the battle alongside Gessler and Wedell, taking the Austrian army in the flank. The battle continues for some time more, but with the Austrians now outmaneuvered Browne's army begins retreating in disarray to the east and south.
The largest engagement of the war so far, the Battle of Prague sees nearly 75,000 Prussians and 50,000 Austrian troops actively engaged. As with the Battle of Brux, losses prove nearly equal, largely owing to the Austrians' defensive positions on the Moldau, with 8,000 Prussian casualties to Austria's 10,000. While the Prussian army has successfully taken the field and routed the Austrians from Prague, it has unfortunately not managed to decisively destroy Browne's army.