Building so many walls

Last week I talked about how city defensive scaling in Civ 6 is a problem.  Cities get stronger as units get stronger, which is fine scaling, but they also scale so many other ways that it is extremely difficult for the AI to ever take cities once walls go up everywhere.  One thing I missed is that each level of walls also adds +3 to the city strength, which makes the situation even worse.  Instead of needing 3-4 melee units, which is enough at the start of the game, the AI would need ~60 melee units to take a modern city with full walls built.  That is too much.

This is an issue of systems, not just individual numbers.  You can't give full scaling off of a single value and then add on tons of other scaling systems too - things get totally out of whack.  A system where cities were super vulnerable without infrastructure but scaled by building more and more walls could work.  A system where cities scale by matching unit strength also works.  A system where both happens is a disaster. 

The problem is that taking late game cities is a brutal slog for the player, with sieges taking forever even once you have destroyed all the enemy units.  For the AI, sieges are just impossible and they can't win.  (If you have played recently you may have seen the AI take cities in the mid or late game occasionally - this is almost certainly because of a bug that can reduce the strength of cities to as little as 10, even if they should have a floor of 70.  Without the bug, the AI is pretty much hopeless.)

So if I want to make the AI a military threat in the mid or late game, I have to get rid of some of this scaling.  The easiest way to do this, I think, is to simply remove the additional Walls types that are available.  Ancient Walls gives a huge boost, no doubt, but even if I only remove Medieval Walls and Renaissance Walls, cities will be much easier to take.  I can also drastically cut down on the health bonus from Urban Defenses too.

But there is something else I needed to do too, and when I tried it the game felt so much better.  I removed the 'cannot attack if it has moved this turn' penalty from siege units, and the change was great.  When catapults are the best unit the AI can build it will spam them, and this always made it a joke.  Every turn it would adjust the position of the catapults, be unable to fire, and end turn.  No matter how many it had I would just burn them down without losses while it moved them around in circles desperately trying to find the perfect configuration.  However, when they could move and fire suddenly they were dangerous!  My walls took plenty of damage, and in the field catapults weren't good, but at least they did *something*.  If the AI could handle planning around siege units being unable to move it would be fine, but it can't, so I need to change things so it doesn't have to.

In the base game the established wisdom is that siege units are bad - just build more melee units and Battering Rams to smash down walls.  With this change, I still don't think siege units are amazing, but I think it is extremely reasonable to build a few.  I also hope that the dramatic reduction in city toughness will allow the AI to fight more effectively - it won't affect human players that much, but it should make it possible for AIs to conquer territory and put up a better late game fight because they just have so much stuff.

Now to play through another game and see how it all shakes out when taken together.  You can only theorycraft these changes so far, that much is for sure.