My friend, and many other players have had this issue where the game starts slowing down and performance degrades past a certain point in the game. This problem happens on both older and newer computer, no matter their specifications. The issue seems to have appeared after Entrenchment. We are still unsure whether it happenned after the expansion or a following patch. The problem, though, is very real and multiple people are unable to enjoy this nice game. There used to be a few threads about this, but they have all become inactive and forgotten, the issue seemingly ignored. Last I know, someone from Ironclad said they were looking into it, but were not able to reproduce the bug. I would like to know if any progress has been made towards finding a solution. If none could be made, my friend and I would gladly volunteer to run whatever tests Ironclad deems helpful in figuring out the cause of the slowdowns.

Edit: I am currently in contact with a member of Ironclad Games' technical support and will post any update related to this issue in this thread if anyone is interested.