Cactus Game Design Message Boards

Yes.  If the fortress is in a location targetable by the band (territory, generally), then the character is in territory.

Unless the fortress specifies otherwise, they can be affected by abilities as if they were in territory.

EDIT: The player WITH Stronghold can band out of it; opponents cannot, as the contents are protected from their cards.

Thank you sir... We were questioning if there was any game rule keeping him from pulling heroes out outside of the preparation phase. But I never did find an entry about it.

Players adding and removing characters from fortresses can only take place during prep phase, unless an ability says otherwise (just like you can only D3 at the start of your turn, unless an ability lets you draw another time or for more cards).  Normally, those abilities are on the fortress themselves, but without protection the contents of fortresses are able to be targeted the same as any other card in their location (see: DD emptying a Fishing Boat).