The conduct of Prussia, in thus rushing into hostilities, without waiting for the advance of the Russians, was as rash as her holding back from Austria, during the campaign of Austerlitz, had been cowardly. As if determined to profit by no lesson, the Prussian council also directed their army to advance towards the French, instead of lying on their own frontier--a repetition of the great leading blunder of the Austrians in the preceding year. The Prussian army accordingly invaded the Saxon provinces, and the Elector, seeing his country treated as rudely as that of Bavaria had been on a similar occasion by the Austrians, and wanting the means to withdraw his own troops as the Bavarian had succeeded in doing under like provocation, was compelled to accept the alliance which the Cabinet of Berlin urged on him, and to join his troops with those of the power by which he had been thus insulted and wronged.
No sooner did Napoleon know that the Prussians had advanced into the heart of Saxony, than he formed the plan of his campaign: and they, persisting in their advance, and taking up their position finally on the Saale, afforded him, as if studiously, the means of repeating, at their expense, the very manoeuvres which had ruined the Austrians in the preceding campaign. In a word, he perceived that the Prussian army was extended upon too wide a line, and the consequent possibility of destroying it in detail. He further discovered that the enemy had all his principal stores and magazines at Naumburg, to the rearward, not of his centre, but of his extreme right; and resolved to commence operations by an attempt to turn the flank, and seize those magazines, ere the main body of the Prussians, lying at Weimar, could be aware of his movement. The French came forward in three great divisions; the corps of Soult and Ney, in the direction of Hof; Murat, Bernadotte and Davoust, towards Saalburg and Schleitz; and Lannes and Augereau upon Coburg and Saalfield. These last generals were opposed sternly, at Saalfield, by the corps of Prince Louis of Prussia. This brave young officer imprudently abandoned the bridge over the Saale, which he might have defended with success, and came out into the open plain, where his troops were overpowered by the French impetuosity. He himself, fighting hand to hand with a subaltern, was desired to surrender, and replying by a sabre cut, was immediately struck down with a mortal thrust. The Prussians fled; the bridge, which ought to have defended, gave the French access to the country behind the Saale. The flank of the Prussian position was turned: the French army passed entirely round them; Napoleon seized Naumburg, and blew up the magazines there,--announcing, for the first time, by this explosion, to the King of Prussia and his Generalissimo, the Duke of Brunswick, that he was in their rear.