The Patriotic War of 1812 was a land mark in Napoleon’s military career because it was his first loss. Before the retreat from Russia, Napoleon’s record was flawless, he was a cunning military mastermind. Napoleon could manipulate the battlefield to his advantage, but The Patriotic War ruined his unbeatable persona. France had a weak truce with Russia, the French nor the Russians abided by their truce, and Napoleon did not want Russia to attack Poland. These led to the Patriotic War of 1812.
Napoleon marched with over 500,000 French soldiers with the intent of destroying 3 major cities in Russia. The Grande Armee was one of the biggest European army’s assembled to that point. The French marched into Russia in 3 gigantic fleets, General Marshal Nicholas Oudinot and his French fleet were stopped in there direct path to St. Petersburg by a small Russian fleet. This tactical move by the Russians led to an inevitable battle in Moscow that would decide the fate of the Patriotic War of 1812.
The Russians attacked the French in small cavalry units while their main army retreated for 3 months, the French were not used to the fierce Russian climate. The Russian main army, and the French Grande Armee, led by Napoleon himself, met in the battle of Borodino, right outside of Moscow, the Battle of Borodino was one of the largest and most brutal battles of the Napoleonic wars. Over 250,000 troops were involved it led to over 70,000 fatalities.
The Russians retreated once more, Russia could replenish their army whereas the French could not, Napoleon marched into Moscow with the Grande Armee and destroyed most of Moscow, but Napoleon could see no victory in sight, Napoleon decided to retreat, this was a disastrous retreat. After Napoleon realized they could not win he tried to reach Kaluga but they were blocked by a replenished Russian army, in the battle of Maloyaroslavets.
Napoleon and the Grande Armee were forced to retreat the same way they had come through the completely destroyed roads of Smolensk, they took catastrophic blows from peasants through guerrilla warfare and the absolutely devastating Russian winter pounded on them, Killing many French troops. When Napoleon entered France there were only one twentieth of the fit soldiers left, the Patriotic War of 1812 was a fierce war with a huge impact on European history. This was the beginning of the end for Napoleon, he was exiled only 2 years later, and his status as an unbeatable tactician was shattered.
http://www.napoleonguide.com/campaign_russia.htm