Answer: Poor planning: not counting at the Russia's scorched-earth policy and unusual bad weather.
Step-by-step explanation:
In 1812, Napoleon Bonaparte was the ruler of France, King of Italy, and master of the European continent. All rulers but Alexander I, from Russia, were subject of Napoleon dictatorship. His pride and ego centrism led him to invade Russia, but he did not anticipate how destructive his decision would prove. His army of more than half a million soldiers was reduced to a band of a few thousand. He had to fight against Russian weather, bad infrastructure, and his bad decision of trusting on Russian land to supply his army, when Russian had their own strategy to destroy their land, so it would not be used by their enemies.