[AI ISSUE/BUG/DISCUSSION] Its a TRAP! Ai disbanding its army...

Not sure what to make of this, but something happened in one of my games and I found it kind of odd. 

So I was playing a game and an AI army was moving towards my city.  My stack of doom was in pursuit, but could not catch up in time.  The city was almost certainly lost, since it had no extra defenders besides city ones.  My stack of doom got with in two squares of the enemy army.  I hit end turn, and instead of attacking the city, which was the intelligent thing to do in that situation, the army mysteriously disappeared.  Trapped between a hammer and a Anvil (or more like a wooden table) I am assuming the AI disbanded the army..... could be a disappearing army bug though.

Anyway, I unfortunately overwrote the save files.     So no proof.... anybody had similar experience?

Also it seems that the AI is pretty stupid when it comes to Wild Lands.  I saw Relias wondering into one, with an obviously underpowered army, never to come out.  The cut scene did say the people who entered disappeared.... Relias must not have gotten the memo.  Then again, other Wild Lands, like the Elemental Chasm place.... it seems the AI avoids it like the plague.  There were two kingdoms bordering that one, and even after I cleared it, it seemed like armies were avoiding it.... could be just a coincidence though.