The Battle of Eylau or Battle of Preussisch-Eylau, 7 and 8 February 1807, was a bloody and inconclusive battle between Napoléon's Grande Armée and a Russian Empire army under Levin August, Count von Bennigsen near the town of Preußisch Eylau in East Prussia. Late in the battle, the Russians received a timely reinforcement from a Prussian division. The town is now called Bagrationovsk and it is a part of Kaliningrad Oblast, Russia. The engagement was fought during the War of the Fourth Coalition, part of the Napoleonic Wars.
Napoleon's armies previously smashed the army of the Austrian Empire in the Ulm Campaign and the combined Austrian and Russian armies at the Battle of Austerlitz on 2 December 1805. Austerlitz forced the Austrians to sue for peace and their Russian allies to withdraw from the conflict. On 14 October 1806, Napoleon crushed the armies of the Kingdom of Prussia at the Battle of Jena-Auerstedt. After a rapid pursuit, the broken pieces of the Prussian army were destroyed at the Battles of Prenzlau and Lübeck and in a series of capitulations at Erfurt, Pasewalk, Stettin, Magdeburg, and Hamelin. Eylau was the first serious check to the Grande Armée and the myth of Napoleon's invincibility was badly shaken.
In late January, Bennigsen's Russian army went on the offensive in East Prussia, pushing far to the west. Napoleon reacted by mounting a counteroffensive to the north, hoping to prevent their retreat to the east. After his cossacks captured a copy of Napoleon's orders, Bennigsen rapidly withdrew to the northeast to avoid being cut off. The French pursued for several days and found the Russians drawn up for battle at Eylau. In a vicious evening clash, the French captured the village with heavy losses on both sides. The following day brought even more serious fighting. Early in the battle, a frontal attack by Napoleon failed with catastrophic losses. To retrieve the situation, the emperor launched a massed cavalry charge against the Russians. This bought enough time for the French right wing to throw its weight into the contest. Soon, the Russian left wing was bent back at an acute angle and Bennigsen's army was in danger of collapse. A Prussian corps belatedly arrived and saved the day by pushing back the French right wing. As darkness fell, a French corps tardily appeared on the French left flank. That night Bennigsen decided to retreat, leaving Napoleon in possession of a snowy battlefield covered with thousands of corpses and many more wounded.