In June 1812, Napoleon led his army into Russia. His army was made up of soldiers from the several nations now under his control. Napoleon expected a short war, to punish Czar Alexander I for his misbehavior in leaving the Continental System. Napoleon took around 600,000 men into Russia. He planned to confront the Russian army in a major battle, the kind of battle he usually won. Alexander knew this, however, and adopted a clever strategy: instead of facing Napoleon's forces head on, the Russians simply kept retreating every time Napoleon's forces tried to attack. Enraged, Napoleon would follow the retreating Russians again and again, marching his army deeper into Russia. Thus the campaign dragged on much longer than Napoleon expected. Furthermore, he had brought few supplies, even by the standards of the short campaign he had planned for, since he expected his army to be able to live off of the land they were in, as was his usual practice. The desperate Russians, however, adopted a "scorched-earth" policy: whenever they retreated, they burned the places they left behind. Napoleon's army had trouble finding supplies, and it grew progressively weaker the farther it marched.
Napoleon's army only engaged the Russians in one major conflict, the Battle of Borodino. Afterwards, on September 14, 1812, Napoleon entered Moscow. The Russians had abandoned the city, which was now on fire and in ruins in conformity with the scorched-earth tactics. With a particularly harsh winter quickly setting in, Napoleon ordered his forces to retrace their path back to France. Yet winter now proved the cruelest foe for what was now an underfed, ragged army. Of the roughly 600,000 troops who followed Napoleon into Russia, fewer than 100,000 made it out.
Napoleon's invincible Grand Army had been destroyed. The Russian Army now flooded into central Europe, taking up Prussia and Austria as allies, and soon the German nationalists rose up in battle as well. To make matters worse, on January 1813 the Duke of Wellington crossed the Pyrenees between Spain and France, threatening to invade France.
In October 1812, a general in Paris almost pulled off a coup d'etat after spreading rumors that Napoleon had died in Russia. In December of 1812, realizing the seriousness of the situation, Napoleon left his army in Russia, as he had previously left his army in Egypt, and returned to Paris. Traveling nonstop by sled and carriage, he made it back to Paris in only 13 days. In early 1813, he raised a new army in France, around 300,000 strong.
By now, however, Napoleon had lost almost all of Europe. During October 1813, at the Battle of Leipzig, nearly every nation in Europe joined in a massive army against the French; in fact, in some parts of Europe, the battle is known as "The Battle of Nations." Napoleon's new army was crushed. Austria, Russia, Prussia, and Great Britain signed a four-way pact agreeing not to negotiate separately, but only ever as a unified foursome, until Napoleon was deposed. In a masterful propaganda stroke, they said they were not fighting against the French people, but against Napoleon.
As Napoleon did what he could with his remaining forces, Foreign Minister Talleyrand took control of a provisional government and started making plans for the restoration of Louis XVIII, a Bourbon. On April 6, 1814, Napoleon finally abdicated his throne and surrendered. He then signed the Treaty of Fontainebleau, which exiled him to Elba. The treaty provided him with 2 million francs a year, and allowed him to retain the title of Emperor, but Napoleon was of course distraught, and tried unsuccessfully to poison himself. Under the terms of the Congress of Vienna (1814-1815), France was basically restored to its pre-1792 boundaries, and the borders of Europe were juggled so that no one nation would become too powerful. The European balance of power was reestablished.