When is it possible to run away?

[Metathron]

Is there a rule for this or is it random?

I was able to run away from Redbeard, but when I tried that with several armies in Greenwort and Marshan Swamp, this option was not available.

Perhaps it's possible when on a continent other than Darion?

The reason I'm asking is I'd like to get a refund from King Mark on some troops I no longer need and could use the money on impossible.

EDIT: The (clumsily translated) fan manual states:

You can run away from a battlefield before the fight termination, but in case of defeat or having run away, you do not receive neither experience, nor money, will lose all armies. However, game on it does not come to an end, you instantly appear in Darion capital and can to continue game further.

Which kinda sounds like you'll have to fight for some time before the run away button lights up...

EDIT #2: I might have been a bit rash in coming to the above conclusions, i.e. I did not wait for enemy troops faster than mine to finish their turns. So I guess that means you can run away from almost anywhere?