Defeat before battle?

I've encountered this (or a similar problem) once, in a Resoln campaign where I had a large army in a high level fortress city (defending.) On the battlefield I had the city defenders and some of my army, but not the rest of the army including Ceresa and another Hero (but bizzarely Ceresa's spirit wolf thing was on the battlefield.) After the battle Ceresa and the other hero were listed as defeated, complete with Injury. The only thing I can think of is there is a maximum limit to the number of units per side in a battle. Sorry I can't be more help.

All the Best.

There is a maximum number of starting points for defenders and attackers in a battle.  There are more starting points for defenders in a city battle, but if you have a lot of militia defenders you can still exceed that if your city garrison is full or overfull (such as when you have nine defenders and then a hero gets defeated and goes to the nearest city - this can exceed the normal 9 unit maximum for garrison).  So, when you are attacking or defending, if you have more units than there are starting positions for your side on the tactical map, you simply won't fit.  Stardock would have to create bigger tactical maps (probably only city battle maps - not sure if this happens with any other maps) with more room for attackers and defenders to completely solve this problem, which I hope they do.

I had this problem as well in a game. It wasn't restricted to cities. My sovereign would die before the beginning of every battle.

Was it a 9-unit army?  I've heard reports that 9-unit armies can cause some problems.

I've battled through a 2 tiered dungeon in a quest, and I'm getting the impression that the deeper level only supports 7 units because another one of my heroes inexplicably died.