thank you for reply, now I understand it better.
I really appreciated your feedback
Last night I join West Empire as mercenary, then when WE send a 600+ army to conquer a Aserai castle, I immediately leave kingdom, then attack the WE army, with only 100+ left, I beat the army, then attack castles
because the castle just got conquered, so it actually doesn't have any garrison( the army didn't entry the castle to drop off garrison) , so yeah I basically took the castle with 0 garrison
now I finally have my first castle hahahaha, now create a kingdom, and form an army, seek peace, then I have time to develop army
thanks again