After my aborted cuirassier rush on Cyrus/Roosevelt, I noticed that Wang/Saladin didn't even have gunpowder or replaceable parts yet, and decided to take my cavalry east and do some damage there. I took 2 of Wang's cities and Hammy Khan dogpiled them. Amazingly that made Wang/Saladin ready to capitulate to me already. Usually the AIs don't let me off so easy. I took capitulation and started moving north again, now with cavalry and cannons.
What followed was one of the longest and most frustrating wars I've ever had. They must have been drafting rifles non-stop since we made peace, because nothing else can explain the number of units they managed to build with only 5 cities each.
I cleaned up their stacks and took Persia's entire core, expecting them to capitulate after each city, but they were still "doing fine on our own". Khan declared on me half way through and their response changed to "we fear your enemies", which gave me some hope. But after I made peace with the backstabbers they went back to being "fine" on their own
I finally gave up and took Combustion for peace, because I had 14 war unhappiness at this point. Cyrus has 2 cities left (he sailed down and took those crappy fishing villages I never got around to settling) and Roosevelt has 3. If they really want to stay independent that badly, that's fine. I don't even want these crap AIs as vassals now. They can just die later when I get tanks.
Amazingly I'm basically at tech parity at this point, even with my economy raped by war weariness and unit maintenance. Hammy Khan is being really pathetic. They have infantry, but they don't even have Physics yet, and I'm about to beat them to it. I've seen Immortal AIs building spaceship parts by this date.
Anyway, I have 22 cities and I just founded Mining Inc. I'll spread that around, industrialize, and smack down these annoying AIs with tanks and bombers.