Quote Originally Posted by xaldub
Ok, I've worked it out and finally got the game to unlock the other factions upon completion of my French short campaign. Immediately after achieving the victory movie I had to elect to play on in that campaign to unlock the other factions. If I simply just chose to stop play at that point, the game doesn't seem to recognise the victory conditions have been met and keeps the other factions locked.

Seems like a bug to me ....
I made the same mistake on my first short campaign with Venice. I'm glad you found the solution, because I was quite confused. However, in the course of my campaign, I had defeated Milan and the Byzantines (as per the victory conditions), so does anybody know why those factions were not unlocked? Of course, in the end I just unlocked them the quick and dirty way.