Meanwhile, however, the pleasant season had mended the roads and dried the swamps. The Russians were refreshed by their long rest, and, children of nature as they were, felt the summer's warmth as a spur to activity. Bennigsen had by that time about ninety thousand men, excluding the Prussians, who now numbered eighteen thousand. By his delay he had lost the services of his best ally, the inclement weather; but he had at least come to a decision, and forestalling Napoleon's scheme, advanced on June sixth to the Passarge, against Ney's corps, which was the French advance-guard. Ney retreated, and the seventh was spent in manoeuvers which resulted in uniting his corps with the main army. Bennigsen, having hoped to cut off and destroy his division before attacking in force, felt compelled, in consequence of failure, to retreat in turn, and this movement left Lestocq at a dangerous distance to the right. At this juncture Napoleon determined to assume the offensive himself. On the eighth he began to concentrate his troops, and took measures to find the enemy in order to force a battle. Bennigsen had withdrawn beyond the river Alle; Soult and Lannes, with Murat in advance, were sent up its left bank to Heilsberg; Davout and Mortier were to pass farther on, as part of a general movement to surround; Ney and the guard were held in reserve, while Victor was despatched to block Lestocq.
The first shock occurred on the morning of the tenth, in the neighborhood of Heilsberg; for Bennigsen had sent a considerable number of his troops back over the river to feel the enemy. The Russians were slowly driven across the plain, fighting fiercely as they went, until by six in the evening they reached the heights near the town, which had been intrenched. Here they turned, and for five hours hurled back one advancing French column after another until eleven o'clock at night, when, fortunately for the attacking troops,--so at least thought Savary, who was with them,--it grew too dark, even near the summer solstice and in those high latitudes, to fight longer. Next morning Napoleon woke after his bivouac and looked to see his enemy gone, as at Pultusk and Eylau. But this time a repetition of that pleasant experience was denied him. His losses had been so serious the day before that he spent the eleventh in manoeuvers, further concentrating his army before Heilsberg, and despatching Davout to throw himself between Lestocq and Bennigsen, thus turning the latter's right and checking the former, if all went well. This movement determined the character of the whole campaign. It had the desired effect, and on the morning of the twelfth the trenches in front of him were empty. The Russians had stolen away, and for two days they steadily retreated down the Alle in the general direction of Königsberg, until on the evening of the thirteenth they reached Friedland.