On the night before his army number more than half a million men crossed the Neman River in the Second Polish War, Napoleon suddenly came down with wind and cramps from his chicken marengo that kept him from sleeping. While battling his discomfort, he read from one of his favorite classics, The Art of War by the Chinese ancient Sun Tzu. He paused between bouts of painful attacks and contemplated the army he had camped around him. Rather than Sun Tzu's model force of fast, elite troops, Napoleon had assembled the largest army known to man. He had hoped the army would strike fear into Czar Alexander and his generals, forcing them to bend to his will, but the “Little General” in him at last decided victories could not be won with simple weight. After all, many of the battles he had won to bring him here had been against much larger armies.
Napoleon's new army moved with incredible speed across the Russian Empire despite its poor roads. The Russian army under Field Marshall Michael Andreas Barclay de Tolly initially attempted to stop the smaller French force but was defeated. The Field Marshall kept his army from being crushed and fell back to a strategy of scorched earth, but the system of retreat did not stop Napoleon. When the French took St. Petersburg, the Czar and his court was forced to flee, and the disgraced de Tolly was replaced by Prince Mikhail Kutuzov. Napoleon moved toward Moscow, but Kutuzov met him with the bulk of the Russian forces at Borodino. There, in the largest single-day fight of the Napoleonic Wars, more than 250,000 men and 1,2000 cannon fought allout. Napoleon won a close victory, and the Russian army returned to retreat.
Victory at Borodino might have been a Pyrrhic one but for Napoleon's well built supply lines. The forty thousand casualties of the Russians could be replaced, and, though it would require longer to return to maximum strength, so could Napoleon's losses of 30,000. The march to Moscow continued. City governor Count Fyodor Rostopchin suggested that the city be set to torch, but Czar Alexander capitulated rather than seeing another capital fall violently. He met with Napoleon the Poklonnaya Hill and surrendered while Napoleon granted him continued control of the Russian Empire, sans the numerous lands such as Poland and the Ukraine that would be granted their freedom (at least, freedom from Russia, as they would be granted governments friendly to Napoleon's Continental System).
Napoleon spent the next years solidifying his command in Europe, putting down Cossack uprisings, quelling Spain, and pacifying the English, whose economy continued to crumble while rebels stirred from the French-backed Irish. He later turned back to expansion, taking Constantinople and conquering the Ottoman Empire. This sparked another war with England in which Napoleon would take the Mediterranean (and, most importantly, Egypt) and incite India to rebellion. Napoleon would die of stomach cancer shortly after Britain's surrender of Egypt in 1823, and his son Napoleon II would prove unable to carry on his father's work.
The French Empire would crumble, but the impact of Napoleonic conquest would be felt for centuries. In what had been efficiency, Napoleon had organized people-groups into states, leading to senses of Nationalism and the unifications of Germany and Italy. Smaller groups such as Serbs, Lithuanians, Poles, Basque, and so on, received new levels of self-government. Most notably, Napoleon would free the serfs of Russia, organizing them and creating a new environment of independence that would make the Russian kingdom a leader in the Second Industrial Revolution and a model of capitalism and progress through the twentieth century.
In reality, Napoleon kept his enormous army, which became bogged down with an indecisive flanking battle at Polotsk that stopped him from his march on St. Petersburg. He moved on Moscow, which he took, but found the city in flames. Surrounded by scorched earth and Russian skirmishers and drained of supplies because of his unintentionally long marches, Napoleon turned back to France, leaving much of his Grande Armée to fend for itself. Roughly 400,000 troops would die or become captured, leaving less than a quarter surviving to return to Paris. The loss would cripple his empire and lead to his first downfall in 1814.