The action of Poserna (1 May 1813) was a French victory on the road to Lützen, but one that cost them Marshal Bessières, who was killed by a cannon shot during the battle (War of Liberation).
At the start of the spring campaign of 1813 the Russians and Prussians occupied the Saxon capital of Dresden and advanced west slowly towards the River Saale. Napoleon decided to try and get around their right flank, and advance through Leipzig towards Dresden, with the aim of threatening the Allied lines of communication. This plan ended up triggering the first major battle of the campaign, fought to the south of Lützen.
On 1 May Ney's III Corps and Marmont's VI Corps were ordered to cross the Saale at Weissenfels, and then advance north-east towards Lützen, to cover the right flank of the advance on Leipzig. They were supported by the Imperial Guard cavalry, one division from the Young Guard and two from the Old Guard, all under Marshal Bessières. This meant that they had to cross the Rippach, a stream that ran through a small ravine as it ran north-west and then west before flowing into the Saale to the north-east of Weissenfels. This stream was lined with villages, including (from west to east) Rippach, Grossgorchen and Poserna.
The Russians were already close to the Saale. A Russian cavalry force until General Sergey Lanskoi was on the north bank of the Rippach, with Wintzegorode and Wittgenstein not far behind.
Ney wasn't sure how reliable his new recruits would be, and so he decided to deploy them in a dense column that made them more reliable, but also made then vulnerable to artillery. General Souham's forces were used for the first attack. Lanskoi's cavalry withdrew, but the French advance was then slowed down by the Russian artillery, firing across the ravine.
Napoleon reached the battlefield by about noon, reaching Rippach on the left of the field. He decided to commit the Guard Cavalry to the fight, in an attempt to force the Russian artillery to retreat. Bessières went forward to examine the ground his troops would have to attack across. One of his orderlies was killed while Bessières was talking to Ney. Bessières himself was then hit by a cannonball while returning to his troops, and killed instantly. His body was taken back to Rippach.
Despite Bessières' death, the French were still able to force the Russians back. By the end of the day Ney's forces were based around Lützen, with outposts to the south-east. On the following day Ney was attacked by Wittgenstein and Blücher, triggering the battle of Lützen (2 May 1813).