Recently lost an immortal game. I was on a standard continent map with the Americans, Russia, Rome, and Siam. I executed a longsword rush very nicely and had them on the field before any of the AI. Rome was on my western border and I quickly dispatched his cities as he and Siam (father west) had been fighting for years.
After eliminating Rome both Siam and Russia (to my east) were friendly at first but within 10 turns both had declared war on me. My empire was six cities big with only a small longsword army to defend it. Immortal AI has a ton of units and Russia did not have iron or horses but Siam had elephants and longswords.
I had blocked Russia's early expansion by grabbing a natural wonder city as I was Spain. This immediately got a message from Catherine to stop expanding into her lands. I told her to stick it. This happened very early in the game because I used the gold from the wonder to build a settler and take the city. Until she declared war on me after I defeated Rome she had not expanded from Moscow at all even though there were good lands around her to take. Her invasion consisted of at least 5 archers and 5 warriors with some spearman mixed in. My wonder city fell quickly even with 2 longswords defending and a 3rd rushed in. I also had Oligarchy. Once she took this city she proceeded to settle two additional cities so my assessment of her behavior is this:
1. She set a very long-term plan (at least 40 turns) into motion to build up a force to expand to her preferred first city location by building a force that was overwhelming.
2. After I had defeated Rome she jumped on me and quickly took the city she wanted and placed two other cities.
3. She did a good job of putting warriors and spearman in front and archers in the back. With as many troops as she mustered it was a well executed attack.
To the west Siam rolled into my Roman puppets with longswords, elephants, and catapults. The size of force he had in the hands of a human would have been game over faster than what he did but he still easily took my three Roman cities.
Siam then declared war on Russia and started moving across my former lands into Russian territory. This allowed a CS to take my former wonder city from Russia! I guess everyone likes a city with a big fat Natural wonder in its borders.
I played that game very aggressively on purpose to see if the AI would react and react it did. I really needed at least twice the Army size I had (4 longswords and 2 catapults for offense and a few spearman and warriors) to even begin to defend against the onslaught I faced. Probably playing more cautious and taking out Russia before Rome would have been a better course of action. I smelled blood with Rome weak from wars against Siam but that blunder led to me looking big and bad with nothing to defend myself and the AI took me to the cleaners.
My next game I dropped to emperor and proceeded to win a space race in which I played a game with no wars, a very tiny army until Infantry and launched a space ship the turn or two after Arabia built the Apollo program. I used RA blocking extensively and it was simple to stay entire eras ahead of the AI on emperor.
