It also makes all the map pins on the war maps (of which it adds more as well) react to the progress of the war/independent clearing whether or not you use the tabletop game (or even get personally involved in the civil war). So (if ignoring the tabletop game) you have to take a fort in a hold (like vanilla), THEN take the main city to actually take control of the hold for your faction.
It restores city battles for progression of the civil war. You'll have to read more on how it works yourself, as I don't use this feature personally. You still get to 'fight' the battles you initiate on the board if you so choose (though there's an auto-resolve feature), and can also fight 'defense' battles for places the enemy attacks on the table. It adds an 'option' to control the 'strategy' of the the civil war through what is effectively a tabletop game.
