You can try to cheat and use the auto_win attacker/defender all you want, but it won't work in the fellowship campaign!
To disable it, do the following:
- Open custom_script.txt, located in: ...\Medieval II Total War\mods\Third_Age\data\world\maps\campaign\custom\Fellowship_Campaign
- Find this part and delete it (make a back-up first!):
Code:
;##################### Restrict autoresolve ##################
monitor_event PreFactionTurnStart FactionIsLocal
restrict_autoresolve true
end_monitor
monitor_event FactionTurnEnd FactionIsLocal
restrict_autoresolve false
end_monitor