He died during the opening engagement of the war, at the Battle of Saalfeld. Louis Ferdinand was in command of 8,300 men when he advanced against marshall Jean Lannes' V Corps as they attempted to break out from the passes of Thuringian Forest. In that battle, he engaged a much larger French force (12,800 men), led by Lannes himself. The French held the high ground, while the Prussians had the Saale River behind their backs, which would make a retreat difficult. When he saw his forces beginning to rout, Louis Ferdinand charged the French cavalry. He was killed in combat by Jean-Baptiste Guindey, quartermaster of the French 10th Hussars, after Louis Ferdinand refused an offer to surrender and wounded the French NCO. As a prominent leader of the Prussian court, his death was deeply felt.