Well, hard to believe, but I just gave up, punted and retired. Liz and Justinian just attacked me on the same front, with big 'ole stacks. Including bombardments, and Grenadiers, when I didn't even have those yet. It was in the 1910's, and I had just recently really started to move as a Civ, tech wise, too.
The game was pretty much a disaster from the start. Flood Plains, and my starting spot wasn't that good, IMHO. But, I stuck with it. Big mistake in not turning off barbarians, in this game. All that struggle with them, and it didn't even help me vs the 1910s onslaught.
I had 8 cities, and figured I'd run with that. I will admit, I was going peaceful all the way. But, it wasn't like I was bottom of the barrell on the power graph. I was pretty high, actually. Not many cities or civs would have held up to the swarm of units that just came at me.
I think I'm remembering deep down why I quit playing 6 weeks ago. I'm not sure BTS is for me. I despise the espionage, and the AI seems gonzo. I'm certainly a Noble player at this point, and more like Prince. So, I'm surprised I just got my hat handed to me. Seems much harder than vanilla.
Also, I really need to learn how some can play this in 2 hours, and it would take me 5, 6, or 7 times as long. It wouldn't be so discouraging to have a game go like this one did, if I only invested a few hours, rather than the 8 or more, that I already had.
Edit: I've been a Civ player since the early 90s, but I just don't know about BTS. Is there a good reason you can't turn off espionage, and still qualify for the HoF?
