Battle of Borodino - Wikipedia

On September 7, 1812 the Battle at Borodino began. From the article:

"The fighting involved around 250,000 troops and left at least 70,000 casualties, making Borodino the deadliest day of the Napoleonic Wars. Napoleon's Grande Armée launched an attack against the Russian army, driving it back from its initial positions but failing to gain a decisive victory. Both armies were exhausted after the battle and the Russians withdrew from the field the following day. Borodino represented the last Russian effort at stopping the French advance on Moscow, which fell a week later. However, the French had no clear way of forcing Tsar Alexander to capitulate because the Russian army was not decisively defeated, resulting in the ultimate defeat of the French invasion following the retreat from Moscow in October.

After a series of Russian retreats at the beginning of the campaign, the nobility grew alarmed about the advancing French troops and forced the Tsar to dismiss the army's commander, Barclay de Tolly. Mikhail Kutuzov was appointed as his replacement. In a final attempt to save Moscow, the Russians made a stand near the village of Borodino, west of the town of Mozhaysk. They fortified their positions and waited for the French to attack. The Russian right wing occupied ideal defensive terrain, so the French tried to press the Russian left for much of the battle.

The highlight of the fighting became the bloody struggle for the large Raevsky redoubt near the village of Borodino. The French managed to capture this redoubt late into the day, gradually forcing the rest of the Russian army to pull back as well. The Russians suffered terrible casualties during the fighting, losing over a third of their army. French losses were also heavy, exacerbating the logistical difficulties that Napoleon encountered in the campaign. The exhaustion of the French forces, and the lack of information on the condition of the Russian army, persuaded Napoleon to remain on the battlefield with his army instead of ordering the kind of vigorous pursuit reminiscent of previous campaigns.[9]

Napoleon's Imperial Guard, the only unit on the battlefield that saw no fighting, was available to swing into action at a moment's notice. In refusing to commit the Guard, some historians believe, he lost his one chance to destroy the Russian army and to win the campaign.[10]

The capture of Moscow proved a pyrrhic victory, since the Russians had no intention of negotiating with Napoleon for peace. The French evacuated Russia's spiritual capital in October and conducted a difficult retreat that lasted until December, by which point the remainder of the Grande Armée had largely unraveled. Historical reports of the battle differed significantly depending on whether they originated from supporters of the French or Russian side. Factional fighting among senior officers within each army also led to conflicting accounts and disagreements over the roles of particular officers."