So basically, Imperial Holberg was the regions of Holfried and Holmauer for a long time. There was some back-and-forth, some no-man’s-land going on where the next one out (can’t recall what it’s called) probably flipped back and forth a lot, and the whole thing lasted long enough for the Druj to set up semipermanent siege camps outside Holberg - the Military Council of the day apparently thought the situation was stable, or at least not the biggest fire, and never sent the kind of overwhelming force that the Empire routinely sends to trouble spots today. For a generation-defining span of time, Holberg was this fortified city that could only really rely upon itself and the odd bit of reinforcement from the other League army. The Towerjacks stopped being an army for a while back there and were just the defenders on the walls of Holfried and Holmauer.
Then a few years ago, the stalemate broke. First it looked like the Empire was losing - Holmauer was ground down, the last bastions were under siege - and then the Empire duped the Druj into thinking they were pulling the armies out, the Druj bet the farm on storming the walls, and the Empire turned around and painted the whole territory with Druj blood in a stupendous strategic reverse. The Druj were basically baited into shooting themselves in the face with their own magical weapons of mass destruction. The battle was a bloodbath - for a few months, back there, there was a curse that magically contaminated any liquid that hadn’t been deliberately purified, down to literally raining poison out of the clouds - but when the dust settled the Druj horde had been practically annihilated.
In the past few years, Holberg has seen a resurgence unknown for a good couple of generations and practically longer. Work after great work has been done on Holberg - massive investment has been made into the rebuilding effort, to the point that what’s being rebuilt these days is likely more like what people imagine that they should have had, without really any reference to what they actually had before the invasion! Fairly shortly after the glorious victory over the Druj, the cities of the League were joined together by a massive road network (in Civ terms, the Empire completed a Wonder) and there is an absolute economic boom going on. Holberg has transformed from a permanent grim state of siege where the only ventures outside the walls were commando raids into a blasted wasteland that Should Be Ours Dammit, into a land of opportunity.
Of course, the Druj are not far away. Really not far away. The other side of the river on the east of the territory is Druj heartland, and of course they infest the Barrens to the south and east like vermin in a roach motel. One day they will be be back, to try once more to claim that which they never could.