What three political / military mistakes led to the downfall of napoleon and the empire he built?

Napoleon made three heavy mistakes "in the Continental System, in the Peninsular War and in Russia's Attack".

Explanation:

The Napoleon's policy for preventing trade between Great Britain and continental Europe is called as "the Continental system " in order to destroy Great Britain's economy. But it raised severe economic strain to Europe and stressed relationship with the Europe leaders.

The Peninsular War proved to western powers that it was possible to defeat Napoleon and the French army. By depositing the Bourbons and stirring Spanish national sentiment, Napoleon provoked a strong opposition to his proposals, which would later lead to his defeat in Spain.

The most catastrophic mistake made by Napoleon was the invasion of Russia, as it demanded death of 500,000 soldiers of Napoleon and specially destroyed his ambiance of invincibility, which kept much of Europe self-satisfaction.