Short description:
In some cases a battle can end in a tie, but the game will tell you that the battle was lost.
The camp will still be there and has to be attacked again (with at least 1 recruit) before it's really defeated.
Screenshot:
Possible cause:
Sending exactly enough troops to defeat the camp, but not enough to keep at least 1 unit besides your own general alive.
Prevention:
Send at least 1 recruit more
Workaround:
Related:
Original thread(s): 1