Answer:
Cold and hunger
Step-by-step explanation:
The so-called Russian Campaign in France, or the Patriotic War in Russia, was a pivotal point for the dreaded French army, which was eventually massacred by cold and hunger and forced to return to France, pursued by the Russians. On the way home, many men died.
Of the 500,000 Napoleon troops who had headed for Russia, only 27,000 returned. This defeat caused a major change in European politics, as it weakened French hegemony and severely shook Napoleon's reputation as an unbeatable military genius.
Napoleon abandoned his men and returned to Paris to secure his position as Emperor and to prepare resistance to the advances of the Russians. The Russian campaign, which began on June 24, 1812, ended with the taste of defeat the following December 14, when the last French troops left Russia.