I wonder if anyone else has noticed this, but I've found that the game can get a bit confused over enemies/allies, sometimes. A case in point, Ive been playing a Norse campaign in BKB recently and had just taken a couple of provinces in Iberia, and moved on to Morocco. The Spanish (Castillean-Leonese in BKB) were initially my allies. They launched a Crusade one year, used my ships to get the Crusade to Morocco, and the next year they back-stabbed me, trying to take (IIRC) Cordoba from me. That same year the Egyptians counter-attacked Morocco whilst I had the Spanish Crusade sat there. Here's where it goes wierd....

On the pre-battle screen it showed the Spanish as ALLIES (even though we were now at war), and true enough, in the battle itself they deployed as attackers and my cursor rollover was red, so they were enemies. Anyway, they ran away once they saw the size of the Egyptian horde.

A little later on, the Spanish sued for peace as "it benefitted neither party". Their Crusade was still stuck in Morocco, and this time the Egyptians AND the re-emerged Almohads attacked. Pre-battle screen showed me on one side, the other three on the other side, with the usual note that the Spanish have also joined the battle and intend to take the province for themselves (which was a bit optimistic, they had been wittled down to about 50 men by now, and the combined Muslim forces were over 6000..... ) However, when the battle started, they deployed as defenders, and had the yellow rollover as expected.

So basically it looks as though the pre-battle screen stage can get it wrong, though the battle itself does seem to be true to the actual strategic situation. Confusing, nonetheless.