“The longer things are going according to plan, the worse it’s going to be when they fall apart.” – Murphy’s Laws of Combat.
“Murphy was an optimist.” Murphy’s Law Corollary.
The trouble with combat offensives going smoothly is that something almost always happens to disrupt them. See the Battle of the Bulge, or Russian Winter 1942 for historical examples. Granted, Valkyria Chronicles 4 is a game, so this sort of setback should almost be expected (else the game would be much shorter) but it’s certainly not a development without historical parallels.
Neither, unfortunately, is the Empire’s treatment of “collaborators”. VC4 is a rare game that doesn’t shy away from a lot of the negative aspects of war, even if the tone can be uneven at times.