What events led to Napoleon's defeat and the fall of the French empire

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.

Napoleon said that if there was an army that he could not defeat, the French Empire would fall. The Russians in the end defeated Napoleon's army causing the fall of the French empire.