The combat of the Bobr or Lowenberg (21 August 1813) was the first occasion on which Napoleon was frustrated by the Trachenberg Plan, in which the Allies had agreed not to risk a battle against the Emperor in person (War of Liberation).
On 14 August Marshal Blücher prematurely crossed the armistice line in Silesia and began to advance west. After briefly considering a move south to attack the Austrians in Bohemia, Napoleon decided to join his forces on the Bobr, and try and defeat Blücher.
By the evening of 20 August Blücher's army was on the east bank of the Bobr, facing Löwenberg (now Lwówek Slaski). On the opposite side of the river Ney (III Corps), Lauriston (V Corps) and Macdonald (XI Corps) were spread out between Löwenberg and Bunzlau (modern Boleslawiec), a few miles to the north. Marmont (VI Corps) and the Guard were approaching from the west, and Napoleon was at Lauban, where he put in place attacks for a full scale attack on the following day.
On the following day Napoleon was to be disappointed. The French captured Löwenberg without any problems, and at noon V Corps crossed the Bobr over the bridges in the town, followed by XI Corps. As they advanced towards the heights on the east bank of the river, Blücher retreated. Yorck's corps was pushed back along the road to Goldberg (Zlotoryja, ten miles to the south west of Liegnitz)
Further to the north III Corps and VI Corps crossed the Bobr at Bunzlau, and pushed by General Sacken's Russians.
Napoleon misinterpreted this move as demonstrating a lack of confidence amongst the Allied commanders, and that they had assumed the French would retreat without risking a battle so far east. Instead if was part of a deliberate Allied plan - no individual Allied army was to risk a battle with the Emperor in person.
On 22 August the French continued to push east, fighting a skirmish between Lauterseifen and Pilgramsdorf. Blücher retreated behind the Katzbach. However the French pursuit was halted by news from Dresden, where St. Cyr found himself facing a considerable Austrian and Russian attack. As a result Napoleon decided to return west to deal with the threat to Dresden, leaving Marshal Macdonald in command of a new Army of the Bobr (III Corps, XI Corps and V Corps).
Over the next few days Napoleon won the battle of Dresden (26-27 August 1813), his most impressive victory of the entire 1813 campaign, but at the same time Macdonald suffered a defeat on the Katzbach (26 August 1813), largely negating the results of that victory.