The French invasion of Russia, also known as the Russian campaign, the Second Polish War, the Army of Twenty nations, and the Patriotic War of 1812 was launched by Napoleon to force the Russian Empire back into the continental blockade of the United Kingdom. Napoleon's invasion of Russia is one of the best studied military campaigns in history and is listed among the most lethal military operations in world history. It is characterized by the massive toll on human life: in less than six months nearly a million soldiers and civilians died.
On 24 June 1812 and the following days, the first wave of the multinational Grande Armée crossed the Niemen into Russia. Through a series of long forced marches, Napoleon pushed his army of almost half a million people rapidly through Western Russia, now Belarus, in an attempt to destroy the separated Russian armies of Barclay de Tolly and Pyotr Bagration who amounted to around 180,000–220,000 at that time. Within six weeks, Napoleon lost half of the men because of the extreme weather conditions, disease and hunger, but winning the Battle of Smolensk. The Russian Army continued to retreat, under its new Commander in Chief Mikhail Kutuzov, employing attrition warfare against Napoleon forcing the invaders to rely on a supply system that was incapable of feeding their large army in the field.
The fierce Battle of Borodino, west of Moscow, was a narrow French victory that resulted in a Council at Fili. There Kutuzov decided not to defend the city but to a general withdrawal to save the Russian army (At the time, Moscow was a very important city, but not the capital of Russia; from 1732 to 1918, Saint Petersburg served as a capital). On 14 September, Napoleon and his army of about 100,000 men occupied Moscow, only to find it abandoned, and the city was soon ablaze, instigated by its military governor. Napoleon stayed in Moscow for five weeks, waiting for a peace offer that never came. Because of the nice weather he left late, hoping to reach the magazines in Smolensk by a detour.