The AI is limited in that it has no notion of whether it's fighting a purely defensive war (where it's units literally only defend), or a defensive war where it has to offensively eliminate attacking units. It simply errs on the side of defensive wars which involve booting the invaders out, rather than dying slowly.
If the AI is forced into a "die slowly" war, it probably means that it's playing at too high a difficulty level, it should find an easier human to play against.
To put it as simply as possible: I don't care what the AI does once it has already lost the game. The AI always plays as if it hasn't lost the game. When playing at a difficulty where the AI has lost from the start, you tend to get poor AI performance, WHAT ELSE are you going to get?
That was basically a design decision: The AI always plays as if it hasn't lost the game. I decided it was not worth the effort to have the AI determine when it has lost the game and then to implement plausible sets of "spiteful strategies". I rathered spent my time implementing as many "winning strategies" as possible.
You know part of the problem is? Once a human has lost THEY JUST LEAVE THE GAME. And part of what I did was try to make the AI play like humans, but I DON'T KNOW WHAT HUMANS DO once they've lost the game but are forced at gunpoint to play on (ANY VOLUNTEERS?). That also makes it hard to implement credible strategies
![lol lol](https://www.realmsbeyond.net/forums/images/smilies/lol.gif)
. Personally I think the "Apathetic response" is as good as any.
(AND DO YOU HAVE ANY IDEA HOW MUCH HATE I WOULD GET IF THE AI SLAVED ALL IT'S CITIES DOWN TO SIZE 1 TURNING THAT POP INTO DEFENDERS? IT MAY BE THE MOST USEFUL THING TO DO WHEN DYING, BUT GOOD GRIEF, I'D HATE MYSELF, THAT'S A LAMEEE SPITEFUL STRATEGY)
And yes there are some fringe cases where it's worth stacking up defenders and hoping the enemy suicides their army or goes away, but the AI is innately terrible at identifying fringe cases, it's strategic/tactical comprehension is extremely low resolution compared with humans.