Napoleon was one of the greatest military commanders in history who conquered much of Europe through military victories. He introduced reforms across Europe that included establishing law codes and abolishing feudalism. However, he ruled as a dictator and centralized power in France through a vast secret police network and state control of the press and expression. After becoming emperor in 1804, Napoleon continued expanding his empire through war but met resistance. His invasion of Russia in 1812 ended in disastrous defeat, contributing to his eventual defeat and exile.