Questions: What strategic mistake did Napoleon make when invading Russia?

The answer is C. not preparing for the harsh Russian winter

While Napoleon may have underestimated various aspects of the Russian campaign, the size of the Russian army was not the primary strategic mistake. The Russian strategy involved retreating and scorched earth tactics rather than direct confrontation.

Although the loyalty of Napoleon's allied forces was a concern, it was not the critical factor that led to the failure of the invasion. The primary issue was logistical and environmental.

This is the correct answer. Napoleon's Grand Army was not adequately prepared for the severe Russian winter. The lack of proper winter clothing, supplies, and the harsh weather conditions led to massive casualties and contributed significantly to the failure of the campaign.

While intelligence and reconnaissance are always important, the main strategic error was the lack of preparation for the winter, which had a more devastating impact on the army's ability to sustain the campaign.