Modern military doctrine was really defined by Nazi operations in WW2, but what’s missed is that the Nazis failed (and for good reason). The depth of supply lines required for an occupation (not just a decapitating strike like France) are immense and infeasible. That’s been proven time and time again by both the US and USSR, and now by Russia.
After the attempted decapitation strike on Kyiv failed, the Russian offensive faltered and had to regroup.