What action taken by Napoleon inflamed this situation and why?

Napoleon's decision to invade Russia in 1812 significantly inflamed the situation, as it led to a catastrophic military campaign that weakened his army and diminished his reputation. The harsh Russian winter, combined with scorched earth tactics employed by the Russians, resulted in massive casualties for the French forces. This ill-fated invasion ultimately sparked a coalition of European powers against him, contributing to his eventual downfall.