"It's not like Russia is big or anything like that"

Explanation: The French Emperor Napoleon declared war and invaded Russia after it demanded French forces evacuate Poland and Prussia. 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 Napoleon’s dreamed-of quick 30-day decapitation campaign ended up into a multi-month slog through the vast emptiness of Russia… and eventually, the retreat and destruction of his army, and his own overthrow and exile by an international coalition of his enemies.