So my civ settled into full-blown builder mode, my captured cities getting up to speed with granaries, forges, libraries, universities, and happiness buildings as necessary. I got a very late Colossus in Arbela, and a pile of wonders in the capital just for lack of anything else useful to build there: Chichen Itza, Angkor Wat, Hagia Sophia, Spiral Minaret. Also Oxford University, which I didn't realize was a national wonder; that locked Persepolis out of building any further national wonders but it was certainly the right choice anyway.
Meanwhile, I sent out caravels that made contact with the two missing civs. I'm up by a half-dozen techs on each of them, and toss one to America to fill in a couple techs that I was missing. I also sign Open Borders with each. And I built two last settlers to fill in the northern tundra area.
I researched to Liberalism, grabbing Printing Press for free, then to Nationalism to rush Taj Mahal with a Great Engineer. Liberalism's civics looked tempting, but after I got them, I just couldn't make any switches.
At this point, I'd been running Representation / Bureaucracy / Slavery / Organized Religion for ages. It felt like I should be making changes to more modern civics (like Republic in Civ 3), but it just didn't seem worthwhile. I was relying on the happiness from Representation bigtime, and still didn't really have enough towns to leverage Universal Suffrage. Bureaucracy's boost was accounting for a quarter of my overall research, enough that Free Speech wouldn't make up for that economic loss and I really had no need for the culture from it. Serfdom and Caste System didn't offer anything over Slavery; for economics I still hadn't gotten any civic techs; and the building boost from Organized Religion was just huge with my civ in builder mode.
I researched to Divine Right which founded Islam (in my mostly-useless tundra city that was founded just to grab the Silver up there; you can see it in the next screenshot.) I also planned to use my latest Great Engineer to rush Versailles in my southernmost city, but it turned out that Versailles costs 800 hammers and the Engineer is only good for 600. So instead he rushes the Sistine Chapel in my tundra city, to get the border expansions to pick up that silver. (Who says you can culture bomb only with Great Artists?) For some reason, the Engineer only goes for 540 hammers in my tundra city, but a couple of forest chops finish off the wonder. (Later I read on Civfanatics the formula for GEng shields: 500 + 20*pop in the city, all unaffected by any hammer build multipliers.)
With the founding of Islam and the capture of a Hindu city, I now had three religions to play with, and spread all of them all my cities with missionaries and built temples.
My next Great Engineer (that's three in a row even though the chance is only like 25%) did indeed go ahead with the Versailles plan, which I realized after the fact was probably pretty silly, spending the GE and 200 shields of Kyoto's real effort to save like 8/turn upkeep costs.
My next research plan was a beeline to Biology and Medicine, as that seems like the biggest growth flashpoint in this area of the tech tree (similar to railroads in Civ 3 though not as dramatic.) I had no need for military techs with Montezuma several techs behind (lacking Gunpowder still).
1655 AD was the date I finished researching Medicine. It's pretty funny that Environmentalism, the most maligned civic in the game, turned out to be my first ever economic civic (I'd never bothered to research any of the other economic techs.) It actually fits well with my game plan -- I've built lots of farms everywhere, and I've got plenty of happiness thanks to three religions, but health is what my cities need most. With all the extra health, I'll grow my cities through the roof and look to specialists to run my economy.
Also, I'll take the chance to double-up on civic swaps by finally going to Free Religion. With most of my cities being nicely built up now, I can trade off from Organized Religion to get the happiness.
This whole situation derives from how vastly different terrain management is in Civ 4. In Civ 3, the primary terrain tradeoff was food versus production, while you'd just take whatever commerce the terrain gave you. And managing that tradeoff was quite easy: just set up a city's tiles to provide enough food for its cap at size 6 or 12 or 20 and mine everything else. With Civ 4, the chief terrain tradeoff is food versus commerce, while you tend to take whatever production the terrain gives you: really just hills and special resources, since the other options to increase shield production are either pretty weak or come late. I erred badly on the side of food in this game.
Monty up and declared war on me again, and that's a BIG stack:
I'd been building some Grenadiers for just such an eventuality, and presently started 3 turns of research on Military Tradition. Incidentally, I noticed a way to sort-of prebuild military units -- I had a couple Horse Archers in production and the build orders got automatically upgraded to cavalry.
Anyway, Tokyo can put walls up just in time (yeah yeah now I know they don't stack with cultural defense), and I've got three Grenadiers and a half dozen elephants and swordsmen in the city. A gigantic bloodbath ensues, and when the smoke clears, there's five Aztec units left standing in my ex-city.
I built cavalry and researched Replaceable Parts, and recaptured Tokyo easily. Then I started razing Aztec cities with cavalry and cannons, but after two razes, war weariness had skyrocketed to 14 in my largest cities and it'd take me quite some turns to put together a stack capable of razing Tenochtitlan, so I made peace.
During that war, I had founded Bactra there and *culture bombed* in it with a Great Artist, but even that left Tenochtitlan's culture still dominant in the area! OK, I've still got a fair bit to learn about how that works. Combat settlers have certainly been nerfed from Civ 3. Bactra would build Globe Theater and Hermitage and run six artist specialists, eventually taking control of its full 21 tiles except for the one that overlapped with Tenochtitlan's 21, but that sure took a long time and wasn't at all worth the economic drain.