I'm looking at the save, so I'll toss in a few comments.
Most of the cities are close to their happy caps, but they can all be stagnated when that time comes. I wonder, should Moscow run its 2 Scientists? Unit costs are already hurting, so I imagine that we'll end up pushing the slider even further down. Or should we try to stagnate to maximize production in our cities because we're pushing for war?
We currently do not have any Buddhist cities, so we can't make that conversion yet. Only two of Khan's cities have Buddhism, so I think that, if we made a concentrated effort, we could get him to go Taoist, but I'm not sure that that would be the best use of resources. Just throwing it out as an option, though.
War-wise, what's the plan? Going after Capac seems like it might yield the best dividends. His border cities are right up against our culture, but they are on hills. Taking Tiwanaku seems especially important because it would grant us two happiness resources (gold, which the city is unfortunately settled on top of, and sugar that already has a plantation.
If we attack Inca, I feel like a two-pronged strike might be best. The main force goes for Tiwanaku, while another strikes Huamanga. I think we'll want a large mounted force for two reasons: Flanking. Both cities are on hills and will have at least one Archer. Lacking siege, a hit-and-run seems like the best bet. Second, both cities can be reached on the first turn of war by 2-move units. Well, Huamanga could be hit by 1-move units, so the second force should probably include most of our slower troops.
We would want to put roads right up to the border. If we can get both towns on the first turn, obviously Capac can't reinforce them. I think that's important since both are on hills and would be tougher to take. Not sure if we would want to keep Huamanga, though, since it doesn't have much to recommend itself aside from being on a hill.
Hmm . . . indulge me a bit further. Strike Force Tiwanaku, ideally, should have, say, 6 Horse Archers, and a couple of Archers and an Axeman for back-up, and to secure the town once it is captured. Strike Force Huamanga should have any other Horse Archers left over, our Chariots, and a couple of Axemen and an Archer to secure the hill. Once both cities are captured/razed, we can combine our forces and march on Cuzco. That's my plan.
As of next turn, we will have 4 Horse Archers, so we'll want at least two more for SFT, maybe one or two for SFH. We have two old Chariots for SFH. We're a bit short on Axemen and the moment, and we'll want to build 2-3 fresh Archers for the attack, (or maybe toss in a Swordsman or two).
Statue of Zeus: So it's being held onto for cash. Probably best, but if we finished it, would it act as any kind of deterrence against people declaring on us?
Lastly: Our war should be planned to be over very quickly. Any cities we capture will drain us financially, despite whatever riches we plunder. Hopefully, we'll have Currency in hand, but I imagine a long period of economic rebuilding will be required after war.
OK, hopefully my plan isn't too out there. If nothing else, it's just what I would do, so take it with however many grains of salt you like.
Edit 'cuz mc-red posted: I wouldn't do a Monastery just because the science slider is so low, I don't think that 10% will make a difference. I think we want to get our units ready ASAP (composition roughly along my suggestion, perhaps) to get the war started and finished quickly. Hmm, if you can really get Construction for Drama, that might be nice. War Elephants and/or Catapults would greatly aid the war effort, BUT we can probably make it with a mounted army at first. If you can then bribe him into war with Spain . . . that might be worth it, though we'd probably want to try and wait as long as is reasonably possible so that we're ready for our own war, too. Wouldn't do for him to make peace just as we are ready to declare, right?
. But maybe not much could have been done about it anyway.
