Is this really a new lesson? I thought that was common knowlegede since WW2 especially with the events of the Eastern Front.
Both Russia and the US learned expensive lessons in Afghanistan fairly recently. And yet here they are engaged in conflicts in Ukraine and Iran that don't seem to go as they planned.
By contemporary lesson I assume she means similar lesson but more recent and keeping modern world/logistics in mind.
Napoleon
What he didn't anticipate was how bad the roads in Russia would be and how long the Russian army would retreat along them. You can't resupply an army that is marching on a narrow dirt road through a forest because it's blocking its own supply lines.