As there is no section for custom battles i put this under miscellaneous files.
The zip file, "Custom battles" contain 3 prepared custom battles for you to play.
A huge city siege
A river battle
A fort siege
Your the earsten empire, all parthia, pontus and armenia have formed an alliance to repel the increasing threats of the romans.
Your role is to win all 3 battles as the parthians, it's up to you to use all stratagies you can possibly think of (to be quite honest the battles are not that hard).
If this does not work please tell me because i made these battles with a mod on, if they don't work please tell me otherwise i can't change it.
Extract all 3 files to Rome - Total War/Custom