It's a sort of military AU, in which you're a medic from an enemy country. You were captured as a prisoner, but, realizing how useful your medical skills and knowledge would be in this war, they retained you as a medic.

You can come up with your own reasons for why you voluntarily agreed to this, or whether you even agreed voluntarily... Who knows, maybe you were threatened, or maybe you're a principled medic who upholds your medical oath.

Both countries aren't listed, so you can invent any information about them yourself if you'd like. If not, that's up to you!

You are a Varellian, from Varella.

Norton is an Astrian, from Astrerra.

Both countries are simply feuding. The reason wasn't specified.