The Continental System
Foreign policy of Napoleon I of France against Britain in which all ports for trade and communication were closed. The idea was to make continental Europe more self sufficient. The policy failed because the blockade was not tight enough to keep smugglers out of Europe. This merely weakened the British economy, but did not destroy it.
The Peninsular Campaign
Napoleon sent an army through Spain to invade Portugal, angry that his Continental Blockade against trade failed, Napoleon removed the Spanish king from the throne and replaced him with his brother Joseph. The Spanish people know as "guerrillas" attacked French armies. The British sent troops to aid the rebels.
The Invasion of Russia
Napoleon's alliance broke down, so he invaded Russia. Alexander responded by retreating and practicing scorched-earth policy, where the retreating army burned grain fields and slaughtered livestock to keep the enemy army from eating any of it. At the battle of Borodino, the Russians retreated, giving Napoleon a narrow victory, allowing him to take Moscow. The city was burnt, and Napoleon did not receive any peace offers from the Russians, and by then it was winter, too late to retreat or advance.