I had another space race loss in about 1920AD. Again, I lost to that damned Huayna Capac.
Short story is that I spent the whole game taking over the main continent and then was too weak to attempt a naval invasion of anyone else.
Same here, except Huey launched in 1952.
As I noted in the first spoiler thread, I delayed attacking Washington until I had a sizable army on his border. I knew at the time that was dangerous, but I thought I doing fairly well. As soon as I declared, Washington upgraded his Archers to Longbows. Oops #1.
The battle began in the early 300s and I thought I could get it over with by about 1000. I razed Chicago at the marble isthmus fairly easily but with more damaged troops than I had expected. I had planned to raze all of his southern cities, but I noticed that Philadelphia was the Confucian holy city. I decided, against my better judgment, to take it. Long term this wasn't a bad decision but the early jump in maintenance costs caused my economy to tank too soon. I should have just left it until later or taken it and sued for peace while I built infrastructure, but I carried on the war. Oops #2.
Having the holy city I could see all of George's Confucian cities which I assumed were his whole empire. I didn't notice the island off the eastern coast (which turned out to be the Christian holy city -- this explains why it wasn't the same religion as the rest of the American empire. The AI usually don't bother to spread their religions via missionaries to cities that already have a religion.) So I made my plans based on the assumption that George had about 5 cities left. I normally would have sued for peace at this point while my armies were healing, but I thought I could win farily soon. Also had a slight tech disadvantage and I wanted to pillage some of Washington's cottages to fund deficit research, so I continued fighting. Oops #3.
Shortly after I declared, I met Mansa, Huey and Catherine. This puzzled me a little as it seemed too early for optics. This should have raised a red flag that I was dealing with some run away techies on the other continent. Also, Mansa was in a galley, which should have puzzled me more than it did, but I was busy fighting Washington. I used the opportunity to trade techs and didn't really think more about it. Curiosity may have killed the cat, but in this case lack of curiosity killed my civ. I really should have sent a galley or even a work boat out exploring the coast much earlier, but having a daisy chain of islands is such a rarity on continent maps that I have lost the habit of early seafaring. Oops #4 (but really Oops #0 since it was a violation of the law that the first priority is early exploration).
Well, I eventually noticed the faint color of Washington's border off the NE coast of the continent and decided to open up the trade window. I thought he only had two cities left (Wash DC and New York) but in the window I saw Los Angeles, Atlanta and Seattle as well. I immediately extorted a tech for peace since it was obvious I wasn't going to win an overseas war quickly with my current lack of transports. I had destroyed, taken and pillaged Washington's territory to the point where he was no longer a threat, but it was now the early 1300s and my own empire was vastly behind the other continents.
I spent about 300 years building infrastructure, researching and gearing my military for a trans-oceanic conquest. Sometime during this period, I met Qin and Elizabeth and also bought Cathy's world map so I had a pretty good idea of what I was facing. It didn't look good. All of the other civilizations were financial, and I was close to none of them in technology. At this point I pretty much figured I was going to lose but I was determined not to go down without a fight.
In the early 1600s I renewed my war with Washinton (who had founded Islam and Taoism in the meantime). Since Cathy and Huey were both hindu, I turned off my state religion. I would have liked to get a hindu city of my own so that I could join the coalition, but it was not to be. I did join a war with Cathy agains Mansa, and later got Qin to join in, so I thought diplomacy might save my bacon, but I never managed to get above pleased.
I destroyed all but one of Washinton's cities, Seattle, which was on a one-tile island. I really didn't want to waste time and troops with an amphbious assault, so I left him until later. In the meantime, Cathy had reduced Mansa to 2 cities on the west coast of their continent and negotiated peace. Qin had dropped out of the fight sometime earlier so I was alone in a war with Mansa that had not cost a single casualty so far.
I built up troops around his most accessible city, planning on walking overland to take out the other city later. This allowed me to carry on the invasion without bothering to build Galleons. By this point I had rifles but I was trying to get up to infantry and transports before going full-scale war against either Huey or Cathy. I got the first city, but Cathy decided to re-enter the war and took his final city when my troops were one square away. This wasn't a big deal, but I had planned on building airports in both places in order to assist my invasion.
Well, to make a long story short, Huey finished the Apollo program somewhere in the 1850s. At this point I was sure the game was lost since I was nowhere near the point where I could afford to go to war with him. I had riflemen and he had had Mech Infantry for several years. I thought about getting Cathy to attack him, but sometime previously they had formed a defensive pact.

So the only war that was possible on this continent was me against the two most powerful civs in the game? Not going to happen.
Qin had been asking me for several years to join his war with Elizabeth, but I had other things to worry about. Both of them had small outpost cities on the edges of my continent that I had been trying to flip culturally. (I know, I know. But I really liked doing this in Civ III and I haven't quite given up trying in Civ IV even though it is now next to impossible.) Sometime in the early 1900s, I decided to go to war with Liz, just to give me something to do while waiting for Huey to finish his spaceship. I threw large quatities of infantry against her Mech Infantry while her scores of bombers devastated my continent. I captured Dover a turn before losing the game to Huey; the very definition of a Pyrrhic victory.
In spite of my early mismanagement of the American war, I really enjoyed the challenge of this game. I usually get frustrated when there is no hope of turning things around, but this map had multiple challenges to keep me interested even after I realized I was going down. Kudos to the designer.
