Just got my ass beaten with Emperor, with Yara Zaqob of Ethiopia (random). I was ableo to expand to five good cities fairly early, and adopted a religion (missionized from Asoka) that two others shared. Still, even though I had culivated fairly strong alliances with them, they were still quite the negotiator when trading techs. I stayed in the bottom-middle of the pack early on.
I needed to break out, so I made my plan around Ethiopia's UU: musketmen with extra first strike bonuses. I was going to attack Lincoln's America, a middling neighbor, who, while ahead of me in score, was somewhat below me in military tech. I beelined gunpowder to build up an army of them, with 10 cats, and a three nights for recon/pillaging. I attacked, and was on a roll, killing his macemen and longbowmen with ease. I kept on making military units from most of my cities at this point for the duration of the war.
I had taken three cities, when my units were starting to run low and war weariness creeping in. I also wanted to get those new cities online by building up their infrastructure. I decided to sue for peace. Then, the wierdest thing happened. Whenever I clicked on Lincoln's name to negotiate an agreement, his diplomatic screen (you know, the screen with the big face of you AI adversaries), it would not come up. Whereas, if I clicked on any other AI's name, the diplomatic screen would come up to negotiate a trade deal. What is with that? I'm used to the red declaration "We are not talking with you", but he didn't give me that message at all. It took me at least a dozen or 15 turns for Lincoln's face to finally pop up he could sue for peace.
During this process of trying to end the war with Lincoln, Mansa Musa, in second place, with a big tech lead, decided to attack. I move some of my units from the previous front line, to the border cities with Mansa Musa. I don't have that many units at this point to defend Mansa Musa's extremely large stack and secondary medium sized one. Mansa Musa proceeded to take the three cities I had just taken from America, and take two more of my interior cities. I played on for several dozen more turns, my score decreasing as the turns went by. When Mansa Musa had a score of 4000 to my 1000, I quite (it started to really balloon at the end).
I'm not discouraged at all. I plan to try Ethiopia again, do more of what seemed to work for this civ, and less of what didn't. Like:
-Focusing even more on 'bulbing', or maintaining a very high science priority (libraries in all cities, monastaries everywhere, trying for a great engineer and building a war academy with great person)
-Beelining to Gunpowder slightly sooner. This would give me those few extra turns to build up a larger military for my attack so I don't get stretched thin when the war is winding down.
-Focus on pleasing Mansa Musa more, my biggest and most potentially aggressive neighbor (he was of an opposing religion). Though, I'm not sure if this would necessarily help much.
-Focus more on wonder-building. The only world wonder I build the entire game was The Pyramids (I had stone), because virtually everyone was teching faster then me, therefore cutting me of from wonders. A focus more on tech would help.
-Focus on big expansion during the initial push before my borders are locked up. Instead of five cities during this time, I'll look for at least another one. Perhaps even more depending on the situation. I'll prioritize settlers even more, especially when grabbing those last free chunks of good land.
-Take advantage of an early opportunity for advantageous war if it presents itself.
-Remind myself to be as flexible as the situation asks for (I always do this, but those always room for improvement).