This is from Anders Nielson a Danish analyst. The entire thing is good, though focused on drones and the sea change in how warfare has changed. The relevant point he makes is, once territory is taken, the advantage goes to the defense and territory taken, like Latvia, etc. Will likely not be easy to get back.
https://www.youtube.com/watch?v=gZL1KzV54Cw
I once saw a flick “This Land of Mine” about the million mines put on the Danish beaches to prevent invasion.. The war was over and the country would not repatriate their German prisoners. Made them remove them. Half of these untrained prisoners got blown up.