The Continental system
According to Wikipedia The continental system or continental blockade (known in french as Blocus continental) was the foreign policy of napoleon I of France and his struggle against great Britain during the Napoleonic wars. In November of 1806, napoleon ordered a blockade to prevent all trade and communication between great Britain and other European nations, it was also intended to destroy Britain's commercial and industrial economy. Unfortunately Napoleon's blockade was not tight enough. Smugglers managed to bring cargo from Britain into Europe Napoleon's allies disregarded his order in-fact napoleon's brother Louis whom napoleon made king of Holland defied the policy. The blockade indeed weakened British trade but did not destroy it. Britain soon responded with its own blockade. British navy stopped and re-routed the american ships bound for trade with the French. The US was angered and declared war on Britain in 1812. Although the war ended in a draw the war hurt Napoleon more than his enemies, also it weakened the economics of France and the other lands under Napoleon's control more than it damaged Britain.
The Peninsular Campaign
Portugal was ignoring the continental system so Napoleon sent an army through Spain to invade Portugal. Spanish towns protested then napoleon deposed the Spanish king and put his brother Joseph on the throne. The Spanish people were angry with napoleon but they remained loyal to their former monarch. The people were also scared of napoleon because the french revolution had weakened the catholic church in France, but they thought that napoleon would do the same to theirs. Instead of compromising the french attacked church power by outlawing the Spanish inquisition. From 1808-1813 groups of peasant fighters know as guerrillas attacked french armies in Spain. Napoleon didn't want to fight them because they were just ordinary people who ambushed french troops then fled into hiding. The guerrillas started fighting and napoleon lost about 300,000 of his men. In Spain and elsewhere nationalism or loyalty to one's country was a powerful weapon against Napoleon. Like the Spanish guerrillas peoples like German and Italians turned against the french.
The Invasion Of Russia
In 1812, Alexander I became Napoleons ally. The Russian czar refused to stop selling grain to Britain, also the french and Russian rulers suspected each other of having competing designs on Poland because of the breakdown in their alliance napoleon decided to invade Russia. In June, 1812 napoleon and his army invaded Russia as napoleons army entered Russia Alexander pulled back his troops because it was an unequal battle. as the Russians retreated they practiced a scorched earth policy were they slaughter live stock and burn grain fields on September 7th the 2 armies fought in the battle of Borodina after several hours of no-stop fighting the russians retreated giving napoleon a victory that allowed him to take moscow when Napoleon entered Moscow on September 14 he found it in flames Russia would rather destroy the city than give it to Napoleon. Napoleon stayed in the city for 5 weeks because he thought the czar would come to make a peace offering, but no offer ever came. In the middle of october Napoleon ordered his starving army to turn back, russian raiders attacks napoleons starving army, finnaly in the middle of December the last survivors made it out of Russia and napoleon had only 10,000 soldiers left.