OK, page 5 says that if the attacker fails to conquer a land on its first try, it gets a +1 if the attack is continued "immediately". The "plus" continues to grow as high as 3, if the attacker is very unlucky. Does this modifier go away when the attacker finally attacks elsewhere on the same turn? Or does the attacker keep his plus 1,2,or 3 modifier on ALL future combats during that turn?
No, it is just for that particular land. If he attacks another one, it starts at a +0 and will potentially grow if the combat fails in that new land.