Believing that Bennigsen's plan was to reach Elbing and defend his communications with Dantzic, Napoleon issued orders on January twenty-seventh for a countermarch in that direction, to engage him either there or farther to the eastward. The orders given next day to Davout and Augereau show that by swift movements he hoped to attack at Willenberg, break through Bennigsen's center, and scatter his forces right and left. Lannes had been taken ill after Pultusk, and was still an invalid; Savary was therefore put in command of his well-tried corps to bear the brunt of the battle. His business was to cover the line of the Narew for the purpose of assuring freedom of action to the main French army, and with that end in view to attack the Russian corps under Essen, which was menacing it. Three days after the orders of Napoleon were given, his army of a hundred thousand men was in position on a line running in general east and west within the space bounded by Willenberg, Gilgenburg, Mlawa, and Przasnysz, with one reserve of forty thousand on the left, to prevent the loss of Thorn, and another of fourteen thousand on the right. Everything was in readiness for an advance under the most advantageous circumstances, to take Bennigsen by surprise, strike him on his flank, and close the campaign in a single battle. On January thirty-first the final orders were issued for the advance, and the march began. As in Franconia, on the eve of Jena, it seemed as if the victory were already assured, won by the marvelous moving of great bodies of men, this time in the depth of winter.
[Illustration: Map of the Battle of Eylau.]
On what a slender thread hang the fortunes of war! That day a French courier carrying to Bernadotte a particularly detailed account of the Emperor's plan, and orders to advance to Gilgenburg, was caught by the Cossacks. The precious papers were in Bennigsen's hands next morning. The Russian troops were still in a wretched condition, badly clothed, and sustaining life by marauding; moreover, they numbered but sixty-five thousand, Lestocq not yet having come in from Mohrungen. The Russian general saw how he was entrapped, and that he could escape only by a swift retreat. His conduct of the movement was masterly, and on February sixth, though the French columns were not far behind, he had reached Heilsberg. During the day the Russian rear-guard was driven in, and Bennigsen, marching all night, found himself next morning before the town of Eylau, or, more precisely, Preussisch-Eylau, the spot he had selected for a desperate stand in defense of Königsberg. The Russian rear-guard was again overtaken, this time at Landsberg, where Murat arrived with his cavalry on the morning of the seventh. All day the Russians slowly resisted him, fighting bravely under Prince Bagration, and receding steadily as far as Eylau, which they held by a stubborn stand until induced to evacuate it voluntarily by the considerations of gathering darkness and a foe superior in numbers. Their loss during the day was upward of two thousand. When night fell the Russian lines were a short distance behind Eylau, and stretched two miles, from Serpalten on the left to Schloditten on the right. Lestocq, coming up with his Prussians, had reached Rositten, between nine and ten miles away, where he received orders to hurry onward. The French held the town of Eylau; in and near it were the troops of Murat, Soult, Augereau, and just in their rear the Emperor with the guard. Ney was farther to the north and west on the left, with orders to cut off Lestocq. The terrain abounded in lakes and ponds of considerable size, but a black frost had rendered them so hard, and the snow had so completely bedecked them, that they were for the purposes of manoeuvering as available as the solid earth, both for cavalry and artillery.