I just returned from work and loaded the auto-saved from the game  that crashed before I left.

The game loaded directly into a tactical combat with three rock spiders (one giant).  On winning I noticed that the game was from a couple of turns before the crash.

Reloading without exiting the game resulted in a fight with three crag spawns.

Tried again and fight with three crag spawns.

Exited the game, restarted and got the fight with the three rock spiders.

Then reloaded and 3 crag spawns.

All this happened with my leaders army on the same tile and no sign of the other army.

autosave

Edit: Just loaded an earlier save and the tile the combat happened on was a cave from the Pits of Namtur