Reules-Heros at enemy territory

By EinHausrl, in Runewars Rules Questions

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.