The idea that conquering another nation through military means should be quick seems to come out from time to time (not just for this war). I wonder if that has ever happened.
Repeatedly: E.g. the battle of France took six weeks, and the 2003 invasion of Iraq just over a month, never mind things like the Warsaw Pact invasion of Czechoslovakia that was over in 2 days. However, occupation can be a bitch...
Yah there is a huge difference in conquering and occupying a land. Insurgent fighters in occupied lands are very difficult to get rid of - as the US learned the hard way in Iraq and the Russians will in Ukraine.
Nazi Germany and Soviet Russia took Poland in 37 days (people forget that the Soviets and Nazis were allied at the beginning of WWII and had an agreement to split Poland). The Nazis alone took Netherlands in four days, and Belgium in 18 days.
The idea that conquering another nation through military means should be quick seems to come out from time to time (not just for this war). I wonder if that has ever happened.