The French invasion of Russia, known in Russia as the Patriotic War of 1812 and in France as the Russian Campaign, begins on June 24, 1812, when Napoleon's Grande Armée crosses the Neman River in an attempt to engage and defeat the Russian army.

Napoleon hopes to compel Tsar Alexander I of Russia to cease trading with British merchants through proxies in an effort to pressure the United Kingdom to sue for peace.

The official political aim of the campaign is to liberate Poland from the threat of Russia.

Napoleon names the campaign the Second Polish War to gain favor with the Poles and provide a political pretext for his actions.

The Grande Armée is a very large force, numbering six hundred thousand soldiers (including three hundred thousand from French departments).

It is the largest army ever known to be assembled in the history of warfare up to this point.

Through a series of long marches, Napoleon pushes the army rapidly through Western Russia in an attempt to bring the Russian army to battle, winning a number of minor engagements and a major battle at Smolensk in August.

Napoleon hopes the battle will win the war for him, but the Russian army slips away and continues the retreat, leaving Smolensk to burn.

French plans to quarter at Smolensk are abandoned, and Napoleon presses his army on after the Russians.

As the Russian army falls back, the Cossacks apply scorched-earth tactics, burning down villages, towns and crops and forcing the French to rely on a supply system that is incapable of feeding the large army in the field.

The Russian army retreats into Russia for almost three months.

In response to the loss of territory, the commander of the Russian army, Field Marshal Barclay, is replaced by Prince Mikhail Kutuzov on August 29.

On September 7, the French catch up with the Russian army, which has dug itself in on hillsides before a small town called Borodino, seventy miles west of Moscow.

The battle that follows is the bloodiest single-day action of the Napoleonic Wars, with seventy-two thousand casualties, and a narrow French victory.

The Russian army withdraws the following day, leaving the French without the decisive victory Napoleon seeks.

A week later, Napoleon enters Moscow, which the Russians have abandoned and burned.

The loss of Moscow does not compel Alexander I to sue for peace, and both sides are aware that Napoleon's position grows worse with each passing day.

Napoleon stays on in Moscow for a month, waiting for a peace offer that never comes.

On October 19, Napoleon moves his army out southwest toward Kaluga, where Kutuzov is encamped with the Russian army.

After an inconclusive battle at Maloyaroslavets, Napoleon continues the retreat.

In the weeks that follow, the Grande Armée starves and suffers from the onset of the Russian winter.

Lack of food and fodder for the horses, hypothermia from the bitter cold and persistent attacks upon isolated troops from Russian peasants and Cossacks lead to great losses in men, and a general loss of discipline and cohesion in the army.

More fighting at Vyazma and Krasnoi results in further losses for the French.

When the remnants of Napoleon's main army cross the Berezina River in late November, only twenty-seven thousand effective soldiers remain; the Grande Armée has lost some three hundred and eighty thousand men dead and one hundred thousand captured.

Following the crossing of the Berezina, Napoleon leaves the army after much urging from his advisors and with the unanimous approval of his Marshals.

He returns to Paris by carriage and sledge to protect his position as Emperor and to raise more forces to resist the advancing Russians.

The campaign effectively ends on December 14, 1812, not quite six months from its outset, with the last French troops leaving Russian soil.The campaign is a turning point in the Napoleonic Wars.

Its sustained role in Russian culture may be seen in Tolstoy's War and Peace and the Soviet identification of it with the German invasion of 1941–1945.

It is the greatest and bloodiest of the Napoleonic campaigns, involving more than one and a half million soldiers, with over five hundred thousand French and four hundred thousand Russian casualties.

The reputation of Napoleon is severely shaken, and French hegemony in Europe is dramatically weakened.

The Grande Armée, made up of French and allied invasion forces, is reduced to a fraction of its initial strength.

These events trigger a major shift in European politics.

France's ally Prussia, soon followed by Austria, break their imposed alliance with France and switch sides.

This triggers the War of the Sixth Coalition.