Quick war in Russia, in and out, what could go wrong?

Explanation: Napoleon declared war and invaded Russia after it demanded French forces evacuate Poland and Prussia. It was, infamously, a disaster, and led to Napoleon’s first abdication and exile.

Part of the issue was that Napoleon attempted to fight the war as previous wars in Europe with much smaller countries. The capital is generally centrally placed, and once that’s captured, it’s difficult to maintain control of the country. With the Russian Empire… not so much. It’s vast and disconnected, and the central apparatus had developed to maintain control over the hinterlands without need to reroute even important matters through the capital - feudal, in a very real sense.

So when Napoleon sat in Moscow, waiting for the Tsar to send negotiators for peace… well… he fucked up. And the retreat obliterated his once-great army and emboldened his enemies to strike against him.