The AI in 1.12 is flat out broke when it comes to waging war. Its fine fighting other AIs as they are broke too so it evens things out, but against the player it is just crippled. On my current map I setup a me vs team of 4 vs team of 4, all AIs set to Expert. I figured id sit in the corner building up my empire while the 4 vs 4 duked it out, and when one of them was winning (or had won) they would then come after me. That part worked out beautifully and eventually after many hours I had the 3 strongest nations that were teamed all declare war on me within like 3 turns. So here I thought I would get this awesome siege on my territory that I could repel (or at least try to). Instead...

After declaring war on me, none of the three AIs, all of whos territory and cities bordered my kingdom, had even a single unit at my border ready to attack. This was like 1939 poland declaring war on germany and then trying to prep some cavalry to go across the border. This is all the while my whole armies are stationed at the borders to defend my frontier. I waited and waited and eventually the first enemy stack arrived, 5 units, three of whom were spearmen and two were archers. Why on earth would the AI send an incomplete stack? All by itself? So it died a horrible death as expected, and I waited and waited and eventually another stack showed up. 3 units, two of which were spearmen and one was an archer. That AI's military strength at the time was rated 2500. So I kept pressing next turn hoping that eventually the blitzkrieg would show up and I giant wave of enemies would descend upon me. Nope. They kept slowly streaming in one incomplete stack after another, single file, from all three AIs. EVENTUALLY the AI rolled out its giant gun: a stack of 1 champion and 5 pioneers. *facepalm* . This was followed up by 2 champions without any escorts who would then after coming back to life after 10 turns without even having full health charge and attack my main stack all by themselves. The strategy of confuse the player, brilliant!

So eventually I got bored and sent my two main stacks in opposite directions to conquer some enemy cities. I wouldnt raze them, I wouldnt build anything there, and I wouldnt station any units there to defend. Just wanted to see what the AI would do to try to take the cities back. To my surprise (and in hindsight I shouldnt have been surprised) the AI did next to nothing. It initially tried to take back one of the cities, which I let it a few times, only to retake it. It soon after that stopped trying to take them back, even though they were undefended. I went deep into the enemy territory and captured a few cities here and there and then retreated to my homeland. Surely the AI would retake undefended cities deep in its lands, yes? Sadly the answer is no, it went about its business completely ignoring the loss of the towns it once had, even though it had them fully surrounded with other towns it controlled.

So to recap:

AI does not send full stacks to attack, or at least very rarely

AI does not escort stacks with other stacks to create a big attack

AI does not escort champions enough and uses them as just a regular unit, probably treating them as just scouts

AI does not defend its border which it should do at all times, even during peace time

AI does not change attack patterns based on previous results and thus never learning from its mistake (aka always attacks same spot, same way)

AI does not setup multi pronged attacks (attack 2+ different places at the same time)

AI does not retake cities with any priority

I played Elemental 1.0 when it first came out for a few hours. Uninstalled it and waited till FE 1.1 to play again hoping to get the complete and fixed Elemental experience. Im still waiting.