The reason Napoleon couldn't invade Russia was that they would burn there own building and supplies so that Napoleon's army wouldn't have any supplies and then he just gave up.
Choices for the major reason Napoleon’s invasion of Russia failed were:
A. the army was too small.
B. the French lost faith in their leader.
C. the Russians chose to retreat.
D. the army was unprepared for the weather
The answer is C. the Russians chose to retreat.