How did geography play a role in
Napoleon's defeat?

Russian geography had defeated napoleon by being difficult to transport and the land is too cold to survive.

Explanation:

The massive land of Russian is the biggest problem and also the sheer scale of the country and distances causes a major problem.  Russia was snowy in winter and muddy in summer and the super snowy slow down the army troops. In Summer Russia will reach 40 degree celcius and in winter it will go down to -50 degrees. Napoleon's army troops were slow down because of these conditions and these are the reason for his defeat.Russia is the invincible country for the enemy to invade because of its geographical features.

Marshall plan is the answer.