Just started playing Idle a week ago. Played the tutorial and next level a few times and the rest once, until I managed to get the entire tech tree on a level. Started replaying the first level to get the achievement, and noticed that the territories have a way stronger defense, more than triple of the original values. Searched the forum for a thread discussing this, came up empty.
Does the defense get stronger the more APs I use? Are the new values due to a version update? Is there something I'm missing?

Maps were rebalanced with new updates, that's why it changes (probably). Btw, why would you want to replay finished levels? It is better to go next level every time, is it not? Like, almost every map takes ~1 day to win, at least for now, and each new level gives more APs than previous.

I started replaying the levels in order to get the achievements for discovering the entire tech tree.
Other than that, O'm planning on replaying each level before I forget them, in trying to finish them faster by going after key territories.

Btw, why would you want to replay finished levels? It is better to go next level every time, is it not?

To get more AP to get better advancements to better clear the later levels. Especially if you redo the level BEFORE the next tweak & rebalance happens, you have the advantage of knowing where things are so can finish it with better efficiency.

I finished most levels 2-3 times. Though as the tweaks continue, clear time is getting longer and longer, so this is quickly becoming less sustainable/tolerable.