Hey when playing runewars fight for terrinoth (reissue) is just the situation that I'm just standing with a hero in enemy territory now the enemy wants to attack me.

Do I have to take part in the fight or, as I understand it, can I just say "I do not want to fight with the hero", as there would not be any troops in the field.

You might need to ask that in this other forum section: https://community.fantasyflightgames.com/forum/146-runewars/

This is for the Runewars miniatures game, not the board game.