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 Koenigsberg. 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.