Napoleon's Invasion of Russia

Napoleon’s invasion of Russia was a costly campaign which resulted in defeat, and the breaking of his power. Before the start of the conflict, Napoleon read every available book on Russia in an attempt to determine it’s strengths and weaknesses. He also studied the attempts of previous foreign monarchs to conquer this immense country. The campaign took place in 1812.

Sources:
https://www.napoleon.org/en/history-of-the-two-empires/timelines/napoleons-russian-campaign-the-retreat/
https://www.nationalgeographic.org/thisday/jun24/napoleon-invades-russia/
http://www.historyofwar.org/articles/campaign_russia_1812.html
https://www.history.com/topics/france/napoleon