Maybe this gets better at Emperor or Deity (although I doubt it) but it seems the Barbarians wage a better battle than the 'real' civs.
At least the Barbies land a half dozen offensive units on my shores and stand a good chance to take a city if it's poorly defended. They make a decent effort, anyway.
Let's see what the other AI civs have done in my current game:
Romans: Hey, let's land 2 Knights and an explorer(why
) outside a walled city with musketers and a crusader.(WHACK!).
Carthaginians: The vikings just established a city on our shores, I think I'll just move a few catapults next to their city one at a time. (POW!POW!POW!) Then after 10 turns I'll take my best defender out of the fortress that is between the vikings and my capital so they can set up shop there (CH-CHING!)
Aztecs: At least we managed to steal a Viking tech (from our former capital) before laying down and selling out the rest of our cities to viking diplomats.
Sioux: I've got 2 riflemen and a partisan fortified outside that city the vikings just captured in a bloody battle, giving them their first beachhead on my continent. Should I attack their tired forces now? Should I hold my ground and keep them isolated (and hungry, by the way) in their place? No, I'll wait a few turns for them to rest their forces, buy city walls, and bring in some more cavalry and a couple spys... THEN we'll take some potshots at the walls with one of the riflemen (BAM!), and move the other rifleman OFF of that strategicly placed mountain.
Sioux (Again): Uh-oh, those big, bad Vikings just put a cavalry unit in one of my 27 unmanned fortresses... I think I'll put 3 of my best offensive units (cannons) in a stack right next to them, but not even attempt to attack. (THUMP! 3 units destroyed). Repeat twice, but this time only move the cannons up one at a time (THUMP! THUMP!)
Now, I *know* I've got some pretty poor military tactics, but the AI is just awful. One of these days I'll have to do a multiplayer game just to find out how the Big Boys do things.
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There are some who call me...Tim